This manual i s sponsored by the Nat ional Weeds Program (Natura l Her i tage Trus t ) , and the Queensland Depar tment o f Natura l Resources , Mines and Water

C o n t r o l m e t h o d s a n d c a s e s t u d i e s

HymenachneHymenachne amplexicaulis

August 2006

While every care is taken to ensure the accuracy of this information, the Department ofNatural Resources, Mines and Water makes no representations or warranties about itsaccuracy, reliability, completeness or suitability for any particular purpose and disclaims all responsibility and all liability (including without limitation, liability in negligence) for all expenses, losses, damages (including indirect or consequential damage) and costs whichmight be incurred as a result of the information being inaccurate or incomplete in any wayand for any reason.

The Queensland Government supports and encourages the dissemination and exchange of information. However, copyright protects this document. The State of Queensland has noobjection to this material being reproduced, made available online or electronically,provided it is for your personal, non-commercial use, or use within your organisation; thematerial remains unaltered; and the State of Queensland is recognised as the owner.

Project undertaken by Land Protection, Department of Natural Resources, Mines and Water.

Photographs: Queensland Department of Primary Industries and Fisheries, University of Florida, Brodie Akacich, Darryl Assenbruck, Matt Buckman, Arthur Cameron, Kate Charleston, Eleonor Collins, Ann Doak, Greg Cooper, Chris Gardiner, Trevor Hall, Barbara Madigan, Col Middleton, Mike Nicholas, Merv Pyott, Stephen Setter, Damon Sydes, Peter van Haaren, Joseph Vitelli, Leonie Williams, Colin Wilson.

Department of Natural Resources, Mines and WaterGPO Box 2454Brisbane Qld 4001© The State of Queensland (Department of Natural Resources, Mines and Water) 2006

QNRM06267ISBN 1 7417220 9#27864 08/2006

Copies of this publication are available from:Ann Doak Project Coordinator (Pond apple and Hymenachne) Department of Natural Resources, Mines and Water Tropical Weeds Research Centre Natal Downs Road PO Box 187 Charters Towers Qld 4820

Phone: (07) 4787 0610

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ForewordHymenachne is an invasive weed with the potential to have major environmental impacts inmany parts of northern Australia. Introduced as a fodder crop for cattle in the 1980s, this grasshas now invaded wetlands, waterways, irrigation and drainage systems, and low-lyingcommercial enterprises such as sugarcane farms.

Hymenachne poses numerous economic and environmental threats to primary production,water resources, fisheries, conservation and tourism.

In this manual, hymenachne refers to the introduced species Hymenachne amplexicaulis, alsocommonly known as Olive hymenachne, and not the native species of Hymenachne thatgrows naturally in northern Australia.

The National Hymenachne Management Group recognises that we will only be able to gainsome control of this weed through the combined efforts, diligence and commitment of allaffected landholders, communities and all levels of government.

I recommend this manual to all landholders affected by hymenachne, and suggest that thoseat risk of hymenachne invasion make good use of the combined knowledge and experiencecontained herein.

Further, I commend all those who have been responsible, both directly and indirectly, for theproduction of this manual.

Nick StipisChairpersonNational Hymenachne Management Group

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ContentsForeword iiiAcknowledgments v

Section 1: Hymenachne: ecology and threat 1Introduction 2Legal status of hymenachne in Australia 3Physical characteristics 4Reproduction and spread 5History of spread 6Distribution and potential spread 7The impacts of hymenachne 9Native hymenachne 12Ponded pastures 14Other ponded pasture grasses 16

Section 2: Managing hymenachne 19A national approach 20Planning 20

Section 3: Toolbox for hymenachne 25Prevention of spread 26Choosing control methods 27Mechanical control methods 27Land management 28

Manipulating water levels 28Grazing 29Shading 30Fire 31

Biological control 32Aquatic weeds and herbicides 32Chemical control methods 33

Safeguards and label information 33Permits 34When to spray 36

Monitoring and evaluation 37Research into chemical control methods for hymenachne 38

Section 4: Case studies 41Early intervention has reduced the hymenachne problem in 42the Cairns region

Canegrower has spent thousands on hymenachne control 45Government and Landcare are working together: eradicating 48hymenachne from an annual lagoon in the Northern TerritoryDoes chemical control of hymenachne affect water quality? 51Findings from a research project in Mackay, Queensland

The value of hymenachne to the grazier 54

Controlling hymenachne in Horseshoe and Pink Lily Lagoons: 56a collaborative project in North Queensland

Section 5: For further information 51

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AcknowledgmentsMuch of the information in this manual, particularly in sections 1 and 3, has been sourcedfrom Weeds of National Significance weed management guide: hymenachne or Olivehymenachne (Hymenachne amplexicaulis). This document has been integral in theproduction of this manual, and information has been used with kind permission from the Cooperative Research Centre (CRC) for Australian Weed Management and the AustralianGovernment Department of the Environment and Heritage.

Principal authorKate Charleston, Extension Officer, Department of Natural Resources, Mines and Water,South Johnstone, Queensland

Other contributorsDr Shane Campbell, Professional Leader, Department of Natural Resources, Mines andWater, Charters Towers, QueenslandAnn Doak, Project Coordinator (Pond Apple and Hymenachne), Department of NaturalResources, Mines and Water, Charters Towers, QueenslandRod Ensbey, Regional Weed Control Coordinator, Department of Primary Industries, Grafton,New South WalesDarryl Evans, Extension Officer, Department of Natural Resources, Mines and Water, SouthJohnstone, QueenslandDr Tony Grice, Researcher, CSIRO, Townsville, QueenslandAlbert Holder, Pest Management Officer, Johnstone Shire Council, Innisfail, QueenslandVic Little, Senior Land Protection Officer, Department of Natural Resources, Mines andWater, South Johnstone, QueenslandMelissa Setter, Weed Scientist, Department of Natural Resources, Mines and Water, SouthJohnstone, QueenslandPeter van Haaren, District Experimentalist, Department of Natural Resources, Mines andWater, South Johnstone, QueenslandJoseph Vitelli, Senior Weed Scientist, Department of Natural Resources, Mines and Water,Charters Towers, QueenslandNoel Wilson, District Manager, Department of Agriculture, Kununurra, Western AustraliaSteve Wingrave, Regional Weeds Officer, Department of Natural Resources, Environment andthe Arts, Palmerston, Northern Territory

Section 5: For further information 63Contacts 64Reference list 66Appendix 69

Case study contributorsCassandra Chopping, Land Protection Officer, Department of Natural Resources, Mines and Water, Mackay, QueenslandGreg Cooper, Pest Management Officer, Cairns Shire Council, Cairns, QueenslandVeronica Edgar, District Weeds Officer, Department of Natural Resources, Environment and the Arts, Palmerston, Northern TerritoryJohn and Ronda Lyons, Graziers and Land Managers, Wambiana Station near ChartersTowers, QueenslandMerv Pyott, Land Protection Officer, Burdekin Shire Council, Ayr, QueenslandNick Stipis, Cane Farmer and Land Manager, Euramo, QueenslandLeonie Williams, Rural Landcare Extension Officer, Department of Natural Resources,Environment and the Arts, Palmerston, Northern Territory

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IntroductionHymenachne (Hymenachne amplexicaulis)is a Weed of National Significance (WONS).It is regarded as one of Australia’s worstweeds because of its invasiveness, potentialfor spread, and socioeconomic andenvironmental impacts. At the same time,however, hymenachne is valued by graziersas a source of fodder for cattle.

Hymenachne is a semi-aquatic grass,initially introduced into Australia for use asa ponded pasture in central Queensland. Itwas later planted in tropical wetlands inNorth Queensland and the NorthernTerritory, where it has escaped fromcultivation and now seriously threatensnatural wetlands, riparian zones andwaterways.

Hymenachne can form dense stands thatreduce plant diversity and habitat for nativeanimals. It invades permanent water bodiesand seasonally inundated wetlands. Itblocks waterways, potentially causing orincreasing flooding, and threatens waterquality. Hymenachne blocks drainage andirrigation channels and infests crops such as sugar cane.

This manual outlines the ecology and threatof hymenachne, discusses a range of controlmethods, and provides planning tools toassist in weed control. It also covers theimpact of ponded pasture species andprovides some information on nativehymenachne (Hymenachne acutigluma).

The information presented in this manual isbased on a review of published information,a study of field practices, and a survey oftechnical experts and weed managers. Inaddition, the manual contains a number ofcase studies that give practical examples ofhow hymenachne is being managed orutilised in various parts of northernAustralia.

Hymenachne: ecology and threat

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� Hymenachne can invade permanent water bodies or seasonally inundated wetlands

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Legal status ofhymenachne inAustraliaQueenslandHymenachne is declared as a Class 2 pestunder the Land Protection (Pest and StockRoute Management) Act 2002, which meansit potentially has serious economic,environmental and social impacts. Underthis legislation, landholders must takereasonable steps to keep their land free ofhymenachne by controlling and, if possible,eradicating any outbreaks on their property.

Western AustraliaAlthough hymenachne has not been foundin Western Australia to date, it is a declaredP1 weed under the Agricultural and RelatedResources Protection Act 1976 and allmovement of plants, seed, contaminatedmachinery and produce is prohibited.Western Australian legislation has alsodeclared it as a P2 weed. This means thatany hymenachne found must be treated to prevent propagation, and infested areasmust be managed to prevent any furtherspread.

Northern TerritoryHymenachne is declared as a Class B weedunder the Weeds Management Act 2001,which means that its growth and spreadmust be controlled. It is also declared as a Class C weed, which prohibits itsintroduction into the Northern Territory.

New South WalesOn 1 March 2006, hymenachne was listedas a Class 1 weed under the NoxiousWeeds Act 1993. This means that it poses aserious threat to primary production or theenvironment and is not present in the stateor is present only to a limited extent. TheAct also states that ‘the plant must beeradicated from the land and the land mustbe kept free of the plant’. To date, only twosmall infestations of hymenachne have beendetected in northern New South Wales.

VictoriaHymenachne has been declared as arestricted weed under the Catchment andLand Protection Act 1994. This means thatthe plant cannot be sold or traded inVictoria.

South AustraliaAll WONS weeds, including hymenachne,are declared weeds in South Australia underthe Natural Resources Management Act2004. Hymenachne cannot be sold ortraded in South Australia.

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� Hymenachne plants

Physical characteristicsThe cultivar of Hymenachne amplexicaulisreleased in Australia in 1988 was named'Olive' and hence some literature refers tohymenachne as Olive hymenachne. Thiscultivar was named after J and P Olive, theowners of Granite Vale, the property incentral Queensland where hymenachne wasinitially planted.

Hymenachne belongs to the family Poaceaeand the genus Hymenachne. Throughouttropical areas around the world, there areeight species of hymenachne, one of whichis native to Australia. The nativehymenachne (Hymenachne acutigluma)occurs naturally in northern Australia. Moreinformation about native hymenachne canbe found on page 12.

Hymenachne is a perennial grass that growsto 2.5 m tall. It can grow above or in waterwith its roots in the soil. Although its stemsfloat, they are not hollow—they containwhite pith called aerenchyma. On land,erect stems can stand to 1.5 m tall, risingfrom stems that run along the ground. Thestems of hymenachne are hairless, andproduce new plants by rooting at the lowernodes. Stems buried by silt or soil easily reshoot.

Hymenachne has bright green leaves,usually 100–450 mm long, with prominentlight-coloured veins and hairy margins. Theleaf base may be up to 30 mm wide and iscovered with long hairs, whereas the upperpart of the leaf is smoother and narrower. Akey characteristic of this species is that theleaf blade is slightly heart-shaped at its basewhere it clasps around the stem.Hymenachne is considerably larger andmore robust than para grass (Urochloamutica), which is found in similar habitats.

Hymenachne flowers occur in cylindricalclusters (200–400 mm long) at the end of a spike, which may also be branched. Theflower cluster is made up of numerousspikelets that are short-stalked, 3–5 mmlong and lance-shaped.

Hymenachne can survive in permanentlywet areas, provided these are shallow in thedry season. The plant is able to grow inwater up to 2 m, but does not persist whenrooted in water that is deeper than 1.2 mthroughout the year. In North Queensland,hymenachne has been observed growing inwater 3–4 m deep (Csurhes, Mackey &Fitzsimmons 1999).

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� Flowers and seed of hymenachne

� Hymenachne leaves with the characteristic leaf-clasping feature

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Reproduction and spreadHymenachne reproduces from seed andbroken stem fragments. Seed germinationdepends on location and seasonalconditions. On land, hymenachne seedrequires contact with moist soil for 48 hoursbefore germination can take place. Innorthern Australia, the most likely time forgermination is during the monsoon seasonbetween November and March. Seed canalso survive in water and germinate whenwater levels recede during the dry season.

In Queensland, hymenachne generallyflowers from April to June, but has alsobeen known to flower between March and September in very wet years. Massflowering is initiated when day lengthdecreases to less than 12 hours. Seed setoccurs from late autumn to early spring inQueensland, while flowering and seed setin the Northern Territory occurs one to twomonths earlier.

Hymenachne produces large numbers ofviable seed, with reports indicating that asingle flower head can produce over 4000 seeds. John Lyons, owner ofWambiana station near Charters Towers, has used hymenachne extensively in hisponded pastures. He notes thathymenachne has a very reliable strike fromseed—around 98%—while para grass hasup to only 16% viable seed. Graziers havereported good germination of hymenachneby simply throwing seeds into ponds.

Hymenachne seed germination andlongevity trials are being conducted by the Queensland Department of NaturalResources, Mines and Water (NRMW) at theSouth Johnstone Research Station in NorthQueensland. Known quantities of seed are buried at depths of 0, 2 cm and 10 cmand will be retrieved at set times for up to15 years. Initial testing in 1999 found agermination percentage of 85%, with afurther 10% of seed viable but dormant.Results after four years indicatedgermination rates between 20% and 65%,depending on burial depth. These resultsshow that buried seed can still havesignificant viability after four years. This mayhave implications for grazing managementof hymenachne, as livestock can tramplesurface seeds into the soil and contribute tolonger seed viability and future problems.

Other research trials by NRMW staff inCharters Towers found that when seed wasplaced in germination trays and watered byoverhead sprinklers, germination rates werevery low. However, when seed wassubjected to waterlogged conditions for 48 hours, the germination rate was high,which suggests that waterlogging may berequired to trigger germination.

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� Hymenachne can reproduce at the nodes

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Seed is transported downstream duringannual flooding and can also be spread by animals. It is thought that waterbirds,particularly magpie geese (Anseranassemipalmata), either spread seed in theirdroppings or transport seed on their bodies.Infestations of hymenachne at remotemagpie geese feeding grounds not routinelyvisited by people support this theory. Theseed of hymenachne can also be spread inmud attached to animal fur or hooves.

Graziers have contributed to the spread of hymenachne by planting seeds or stemfragments in mud, or by placing them inshallow water. Only a small piece of maturegrass is required for new areas to becomeinfested.

When hymenachne is planted on grazingland, floods and stormwater run-off cantransport seed and plant fragments intopublic waterways, irrigation storagefacilities, sugar cane crops and naturalwetlands. Under natural conditions, floodscan break off plant segments and carry themlong distances downstream. As hymenachneis perennial, the shoots can brown off ifconditions become dry and regrow duringthe wet season.

History of spreadHymenachne is native to tropical regions of South and Central America. It is a seriousweed in Trinidad, Florida and Surinam.

Hymenachne was first imported intoAustralia in the 1970s, with the aim of usingit in ponded pastures too deep for paragrass. Ponded pastures are used to providefood for stock during the dry season, whenother sources of protein have been used.Prior to the release of hymenachne (andaleman grass), ponded pasture systemsrelied on native grasses and the introducedpara grass. Although para grass alsoprovides good forage for cattle, it isintolerant of water deeper than about 60 cm.

Hymenachne was approved for release inQueensland in 1988. Following its officialrelease, the Department of PrimaryIndustries and Fisheries (DPIF) organisedseveral field days to promote hymenachneas a fodder plant. Landholder interest andadoption rate of ponded pastures increasedrapidly, and graziers were quick to obtainvegetative material for themselves as well as colleagues in Queensland and interstate.

Hymenachne escaped cultivation within a few years of being released and, by 1997,dozens of infestations were reported insugar-growing regions (Csurhes, Mackey &Fitzsimmons 1999). It was predominantlyfound in low-lying cane plantations anddrainage ditches throughout the Wet Tropicsregion of Queensland. By 2000, the total area of infestation was estimated to be at least 1000 hectares.

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� Hymenachne can survive in permanentlywet areas

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Hymenachne has also been planted as apasture grass in the Northern Territory alongthe Adelaide, Daly, Finniss and Mary riverfloodplains, and at Arafura Swamp innorthern central Arnhem Land. It has nowspread through parts of these catchmentsincluding important conservation areas suchas Kakadu National Park.

Distribution andpotential spreadThe factors that govern hymenachne’spotential distribution and abundanceinclude climate, water depth, period ofinundation, soil moisture (during dryseasons), light levels, salinity, and soil-waternutrient status. Hymenachne preferstropical, low-lying freshwater wetlands andflood plains. It grows prolifically inwetlands that are subject to high nutrientand sediment influx from upstreamagricultural land, but can also persist in lessdisturbed areas.

As a semi-aquatic grass, hymenachne thriveson clay soils that are inundated during thewet season but dry out to some extent in thedry season. The subsoil must remain moistduring the dry season, as hymenachne canonly withstand short periods withoutmoisture. Consequently, it is found mainlyin low-lying areas along the edges ofpermanent water.

Hymenachne can withstand prolongedinundation by growing above the water.However, it does not tolerate brackish waterand does not tend to grow well in shadedareas. Since light availability is considered a primary factor limiting distribution andabundance, hymenachne is not expected toform extensive stands where native treesprovide dense shade along the banks ofwatercourses. NRMW staff at SouthJohnstone are currently investigating the useof shade to suppress hymenachne.

� Beatrice Lagoon in 1995 after hymenachneinvasion

� Pristine Beatrice Lagoon in the Northern Territory in 1986

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In North, Central and South America, therange of hymenachne extends betweenlatitudes 26°N and 28°S. Climate analysisusing the CLIMEX computer-modellingpackage suggests that climates experiencedin coastal areas of northern Australia aresimilar to those experienced in the plant’snative range (Csurhes, Mackey &Fitzsimmons 1999). Based on its nativedistribution and climate, hymenachne couldpotentially occur in all seasonally floodedwetlands of Australia, including theKimberley Ranges and the central coastalregion of Western Australia; the Top End of the Northern Territory; most ofQueensland’s coastal and eastern regions;and northern New South Wales.

Hymenachne may also spread into semi-arid zones where land is flooded during thewet season and remains waterlogged during

the dry season. Suitable conditions forhymenachne can be created on clay soils by irrigation channels or banks that trapoverland water. Hymenachne is not likely to persist on well-drained soils.

Para grass is estimated to cover 100 000hectares in Queensland and 40 000hectares in the Northern Territory. This mayindicate the potential distribution ofhymenachne, since both species sharesimilar habitat and climatic preferences(Csurhes, Mackey & Fitzsimmons 1999).There are, however, some major differencesbetween the two species. Hymenachnegrows taller and in deeper water than paragrass, and produces dense floating mats thateventually smother other plants. In drierhabitats, hymenachne is not likely tocompete with para grass, which is moredrought-tolerant than hymenachne.

Potential distribution of Hymenachneamplexicaulis

(Data is splined from a CLIMEX prediction.

EI = Ecoclimatic index:

EI < 30 potential forpermanent population low,

EI > 50 potential very high).

� Hymenachne grows prolifically in wetlands� Hymenachne thrives in nutrient rich environments

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The impacts ofHymenachneExotic grasses are an important weedfunctional group. They can have profoundecosystem impacts by altering fire regimes,changing soil properties and hydrology, andreducing biodiversity. They can also replacepalatable native grasses on pastoral lands,compete with crops, and block access topublic areas and amenities (van Klinken et al. 2004).

Numerous economic and environmentalthreats are posed by hymenachne. Theenvironmental threat to wetlands is severe,as hymenachne can outcompete all otherplant species. Environmental effects areclosely tied to the economy. For example,tourism, which generates around $30 million annually in Kakadu NationalPark, is heavily reliant on the appeal ofuntouched wilderness. Similarly, thepotential loss to Indigenous people ofnatural wildlife resources (such as fish andwaterfowl) has both environmental andeconomic consequences.

Hymenachne impacts on a number ofindustries, as summarised below.

Primary productionHymenachne has invaded sugar cane cropson low-lying, poorly drained land in NorthQueensland. This leads to cropcontamination and increased productioncosts. Hymenachne can smother youngcane, contaminate seed cane plots andblock drainage ditches, thereby causingwaterlogging. Heavy infestations can causeproblems harvesting cane. Floating mats ofhymenachne can contribute to stock lossesdue to drowning.

Water resources and infrastructureHymenachne has already invaded irrigationwater storage facilities in the Burdekinregion of North Queensland. Hymenachnemodifies water flow and impedes the flowof floodwater, which can increase floodingin low-lying areas.

� Drains adjacent to cane infested by hymenachne

� Sugarcane invaded by hymenachne (bright green in foreground of photo)

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Large stands of hymenachne can causedecreased water flow, stagnation, increasedlevels of organic matter, passage barriers tofish and increased levels of soil nitrogen.Hymenachne also causes the loss of nativeplant habitat by shading and competingwith native riparian and in-stream aquaticplants.

Floating weed infestations and dieback ofhymenachne during dry periods contributelarge loads of organic matter to the waterbody. This material decomposes andconsumes available oxygen, a process thathas adverse impacts on water quality. Theanoxic conditions that can be createdbeneath floating mats of hymenachne canfacilitate the release of nutrients such asphosphorus from sediments, and this in turnprovides a supply of nutrients for thefloating weed mat.

Floating mats of hymenachne dislodgeduring floods, potentially damaging lowbridges. The Rockhampton City Council inQueensland reports that floating rafts ofhymenachne during floods have dislodgedboats from their moorings, causingstructural damage to boats and wharfs.Hymenachne also has the potential to dragboats under water if sufficient materialgathers on the anchor lines.

Hymenachne can block the foot valves ofpumps and other irrigation equipment. Thepresence of hymenachne—and potentialherbicide applications to control it—incatchments used to collect drinking water isa matter of considerable public concern.

In contrast, hymenachne can act as a filterby trapping sediment and nutrients, therebyreducing nutrient loads from pollutedcatchments.

� Large mats of hymenachne can potentially damage bridges during flood events

� Hymenachne can block the passage of fish

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FisheriesThe fishing industry is concerned thathymenachne can invade the naturalwetlands that act as nursery areas forjuvenile barramundi. Pure stands ofhymenachne can modify the habitats of native invertebrates and other aquaticmicrofauna, consequently affectingdependent populations of native fish.Hymenachne affects water quality bypreventing the infiltration of sunlightthrough the water column. This limits or prevents photosynthesis and oxygenproduction by submerged aquatic plants,which, in turn, threatens fish habitats andnursery areas.

The high-value prawn industry may also beat risk from hymenachne, as prawns breedin response to natural flood events and anydisruption to natural run-off patterns canreduce their recruitment success.

Ponded pastures can impact on fishmovements, with many ponds acting as fish traps. Fish swim over the banks duringfloods, but cannot escape when waterrecedes. Fishing is affected whenhymenachne blocks commercial fishing nets or impedes the passage of boats.

Conservation and tourismIn Australia, the growth of hymenachne isunaffected by native pests and diseases, andit therefore has a competitive advantageover certain native species that dominateseasonal freshwater marshes. Hymenachnereplaces native wetland plants, and this inturn affects dependent wildlife. While somenative animals may adapt to utilise thisweed, many will not. In either case, thenatural balance is disturbed.

Hymenachne can prevent the recruitment of native trees, and exclude native grassesand sedges that provide food and nestingresources for wildlife. The loss of nativebirds and other wildlife, and thedegradation of conservation areas, impactson tourism and could lead to substantiallosses. Hymenachne reduces aestheticvalues and recreational opportunities.

In the Northern Territory, Olive hymenachne(and, to a smaller extent, nativehymenachne) was used for revegetationfollowing control of another serious weed,Mimosa pigra. This inadvertently led to theincreased spread of hymenachne on thefloodplains and in conservation areas of theNorthern Territory.

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� Hymenachne infestations are potential mosquito breeding areas

� Conservation areas can be spoilt by the presence of hymenachne

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HealthPublic health and safety are at risk, asinfested areas provide an ideal habitat for mosquito larvae. The thick mats ofhymenachne prevent fish from feeding onmosquito larvae, thus allowing mosquitopopulations to increase. The RockhamptonCity Council has expressed concerns aboutthe increased population of two species ofmosquito in the area, which is attributted tothe presence of hymenachne in localwaterways. Hymenachne can increase therisk of drowning, as the thick floating matsoften look like firm ground.

GrazingHymenachne grows in deeper water thanother pasture species. It remains palatablewell into the dry season, providing high-protein cattle fodder. As a ponded pasturespecies, it helps stabilise fluctuations inproductivity that occur due to seasonalvariations in forage availability. In times of drought, the ponded pasture enablesgraziers to maintain herd sizes and helps to prevent land degradation due tooverstocking. The impact of hymenachne on the central Queensland grazing industryis generally considered to be positive incontrast to its value in the Wet Tropics,where other dry season fodder is often ingood supply.

The economic impacts of hymenachne aredifficult to estimate. While there is probablya net gain to graziers who utilise this grass,the cost of controlling hymenachne in areaswhere it is undesirable is expected to farexceed the positive returns.

Native hymenachneHymenachne acutigluma is a native speciesof the genus Hymenachne. This perennialgrass is found throughout the northernAustralian wetlands, and is palatable tostock. In the late 1970s in the NorthernTerritory, buffalo ate so much of the nativehymenachne that there was concern that itwould become extinct. However, itregenerated successfully following a buffaloeradication campaign.

The native hymenachne is similar inappearance to Hymenachne amplexicaulis(Olive hymenachne) and is a trailing grassthat roots at the lower nodes. The stemscan be over 4 m long, containing 10 ormore nodes. Leaves are 15–30 cm long and2–3 cm wide. Native hymenachne does nothave a stem-clasping leaf base, and cantherefore easily be distinguished from Olive hymenachne.

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� Native hymenachne growing in the Northern Territory

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Native hymenachne is dark green. The seedhead consists of a spike, 8–10 cm long,which contains small seed (1–2 mm).Native hymenachne produces few viableseeds; although each seed head contains500 florets, only 1% of these floretsproduce seed (Cameron 2003).Regeneration from seed is more significantin natural stands. After large floods, newseedlings can be found below the highwater mark. Seed production oftencoincides with flooding, which preventsaccess to the plants and makes harvestingseeds difficult.

Native hymenachne has similarenvironmental requirements to Olivehymenachne but is less tolerant of coolweather, which may explain the failure ofnative hymenachne evaluation trials southof Mackay in Queensland.

Studies comparing growth of the twospecies found that native hymenachnegrows more slowly, at lower temperaturesand light intensities. However, at hightemperatures, when light intensity is notlimiting, the native hymenachne exhibitedhigher growth rates than the exotic species(Kibbler 1997).

Studies of both species found that they havesimilar adaptations to flooding:

• Stems rapidly elongate.• Leaves rapidly senesce (die) when

flooded, and submerged stems produce adventitious roots.

• Elongation results from the production of new nodes and the expansion of recently initiated internodes.

In the Northern Territory, nativehymenachne is recorded in areas that arewet for 6–12 months of the year. In drierenvironments such as the Alice Riverfloodplain, which is inundated for less thanfive months of the year, no hymenachne hasbeen recorded.

Native hymenachne is used as dry seasonfodder, especially in the Northern Territorywhere it is more abundant than inQueensland. It has been used with othernative grasses for revegetation, followingmimosa (Mimosa pigra) control onfloodplains in the Northern Territory. If thefloodplain was in good condition, nativegrasses such as native hymenachne werefound to provide productivity gains equal toany introduced species (Searle & Fell n.d.).

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� Native hymenachne (pictured) looks similar to Olive hymenachne but lacks the leaf-clasping characteristic

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Like its exotic relative, native hymenachnehas the ability to produce thickmonospecific stands. Traditional landownersin the Northern Territory control nativehymenachne through systematic burningonce the vegetation becomes sufficientlydry. Regular burning of the flood plains isused to keep fuel loads down, and theremoval of hymenachne promotes thegrowth of highly prized Indigenous foodspecies such as water chestnuts (Russell-Smith n.d.).

Native hymenachne is difficult to propagateand has generally been overlooked forgrazing, in favour of robust exotics thatgrow larger and faster and are more readilyavailable. Given the detrimental impacts ofOlive hymenachne, existing nativehymenachne pasture must be preserved and carefully managed. The potential forexpanding the use of native hymenachne in pastures instead of Olive hymenachnedeserves further investigation.

Ponded pasturesPonded pastures are defined as ‘the practicedeveloped by pastoralists to create anenvironment by either the construction ofbanks or the modification of naturally wetareas, in which fresh water is impounded orused primarily to grow suitable adaptedplant species and produce fodder forgrazing’ (Queensland Government 2001).

Pastoralists in northern Australia have takenadvantage of natural wetland systems forgrazing since the late 1800s. Theconstruction of artificial ponds in dry landareas commenced in the 1930s in responseto the perceived need for improved pasturesfor the pastoral industry in northernAustralia. There was a widespread beliefthat any plant introductions that modifiedrangelands would always be beneficial, andlittle consideration was given to weed risksor environmental impacts (Grace, Gardener& Cameron 2004). The development ofponded pastures accelerated in the 1970swith the introduction of new pasture speciesby CSIRO and promotion in Queensland bythe Department of Primary Industries andFisheries.

The development of ponded pastures hascontributed to the beef industry andcommunity development. The large increasein cattle production in the NorthernTerritory has been attributed to theintroduction of exotic pasture species.

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� Ponded pastures have yielded benefits to the cattle industry K

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Many of the native grasses have shortgrowing seasons and good feed is availablefor only a few months of the year. Theintroduced pastures are more digestible,produce greater biomass, remain greenerfor longer and are generally moreproductive than pastures based on nativegrasses. However the negative impact ofthese developments, through the unwantedspread of introduced pasture species, hasbeen substantial.

Conflicts between pastoral andenvironmental interests are widelyacknowledged in relation to exotic grassspecies. Hymenachne is a prime example of this conflict, where the grass has yieldedsignificant benefits to the pastoral industryin some areas yet is an aggressive invader of natural habitats.

Ponded pasture species usually includeintroduced species. In Queensland, theintroduced species are para grass (Urochloamutica), aleman grass (Echinochloapolystachya cv. Amity) and hymenachne.All three introduced grasses are nowregarded as invasive weeds in naturalfreshwater wetland systems and otherwaterways.

There is currently no legislation dealingspecifically with ponded pasturedevelopment or management inQueensland. However, the QueenslandGovernment considers that thedevelopment of ponded pastures shouldoccur only in areas that are not:

• tidal areas• in or adjacent to natural wetlands• of high conservation or fish habitat

value.

The development of ponded pasturesshould occur only where it can bedemonstrated that there will be minimaland acceptable environmental impacts.Under the current ponded pastures policy,para grass, aleman grass and hymenachnewill not be included in pasture mixesrecommended by Queensland Governmentagencies. In addition, all state governmentagencies will use an integrated education,extension, research and regulatoryapproach to prevent adverse environmentalimpacts and to control the spread of currentponded pasture species.

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� Ponded pasture

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Other ponded pasture grassesAlthough para grass and aleman grass arenot declared weeds in Australia, thesegrasses also pose environmental problemsand are often found in conjunction withhymenachne.

Aleman grass (Echinochloa polystachya cv. Amity)Aleman grass originates from tropical andsub-tropical countries of America—from thesouthern United States of America (USA) tonorthern Argentina—where it is used foranimal forage. It was first tested in Australiafor use in ponded pastures in water toodeep for para grass on properties in centralQueensland. It was approved for generalrelease in July 1988.

Aleman grass is a robust, vigorous, semi-aquatic grass, which produces long stemsthat tend to grow upright or float on thewater surface. The stems of aleman grass are10–15 mm in diameter, up to 2.5 m longand contain 7–10 nodes. The smooth and

hairless leaf blades have a light blue-greencolour, and are 10–25 mm wide and200–600 mm long. The seed head is anopen panicle, which is 150–250 mm longand produces seeds of 4–5 mm in length.

Aleman grass seed is believed to be sterileand the plant can only reproducevegetatively. Each node on the stem candevelop roots. It will grow in water to adepth of 3 m and is adapted to poorlydrained, relatively infertile soil andseasonally flooded sites. Initial growth ofaleman grass is relatively slow and it can be outcompeted by other grasses. However,this plant’s ability to invade deeper waterthan hymenachne and potentially destroycommunities of submerged or floatingnative plants is of concern.

Aleman grass is currently undergoing aweed risk assessment to ascertain itspotential as an environmental threat. The outcome of this weed risk assessmentwill contibute to the decision of whetheraleman grass will be declared a weed inQueensland or remain available as a forage species.

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� Aleman grass with seed head � Aleman grass is a vigorous grass with long stems

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Para grass (Urochloa mutica)Para grass is a native species of tropicalAfrica and South America, and was firstintroduced into Australia in 1884 to controlriverbank erosion. Para grass is a coarse,vigorous, trailing perennial that producesstout runners (stems), which branch androot readily at all nodes.

The root system of para grass is shallow and fibrous. Stems can grow up to 5 m longwhen creeping, and stand 1 m tall whenerect. Leaf blades are flat, 20 mm wide andhairy. Dense, stiff hairs can be found at thebottom of the leaf sheath (the part of theleaf around the stem). At the base of thesehairs is a small ligule—a small, wart-likeoutgrowth that can be viewed with a handlens.

Flowers of para grass are in a terminalpanicle 200 mm long, which branches at aright angle to the stem. Spikelets are about3.5 mm long and are often tinged purple.Flowering time depends on location. Paragrass seeds are small and, despite the largequantity of seeds produced, the number offertile seeds is low.

Para grass is considered one of the world’s worst weeds and is reported as an agricultural pest in 23 crops in 34 countries, including the USA. Itcompetes aggressively with other plants,and its fast growth, high productivity andallelopathic (production of chemicals thatinhibit growth of nearby plants) abilitiesallow it to form a dense monoculture.Studies have shown that when para grassdisplaces hymenachne, it leads to areduction in invertebrate biodiversity(Douglas & O’Connor 1999).

Para grass grows well under warm, moistconditions and has naturalised in manyswampy areas. It will grow in any wet soil,including brackish conditions, but respondsbetter to fertile soils. It reproduces andspreads primarily by stem fragments.

Studies in the Northern Territory haveindicated that exotic grasses contribute tochanges in fire regimes. The changes in fuelcharacteristics caused by invasion of paragrass can increase the intensity offloodplain fires, particularly in drier sites,resulting in detrimental effects on nativewoody plants (Douglas & O’Connor 2004).Such studies demonstrate the need tocontrol current para grass infestations andprevent further spread.

17� Para grass seed head and seeds

� Para grass can survive in shallow water

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With an estimated 100 000 hectares underpara grass in Queensland, elimination ofthis weed is unlikely. Many scientistsbelieve that para grass has largely occupiedits potential Australian range, althoughwithin this range there are still many areaswith little or no para grass. Nonetheless,prevention and control of this grass remainsvital. Like aleman grass, para grass iscurrently subject to a weed risk assessment.

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� Para grass is usually found on the edge of watercourses

� Para grass can destroy waterbird breeding habitat

� Para grass is considered one of the world's worst weeds

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ManagingHymenachne

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S e c t i o n 2

A national approachTo address the current and potential threatsfrom hymenachne, a national strategy waslaunched in 2001 with the vision that ‘theadverse impact of hymenachne is reducedto a minimum’. The strategy’s four desiredoutcomes are to:

• prevent the spread of hymenachne• minimise the adverse impact of

hymenachne• establish and maintain national

commitment to the management of hymenachne

• ensure that this strategy does not trigger the introduction and use of additional species of non-indigenous ponded pasture species.

Historically when valuable plants areprohibited from use, proponents of thoseplants often search for replacements withsimilar attributes. There is a danger that newand potentially more aggressive pasturespecies could be imported or released. Suchspecies must be subject to rigorousassessments of their potential impacts andthe introduction of any ponded pasturespecies with weed potential must beprevented.

The national strategy is documented in theWeeds of National Significance:Hymenachne (Hymenachne amplexicaulis)Strategic Plan and is led by the NationalHymenachne Management Group. Thisgroup comprises agency and communityrepresentatives, and is responsible foroverseeing and monitoring theimplementation of the national strategy.

PlanningAny control program should be plannedwell to ensure that the best possible resultsare achieved with minimal cost and effort.To do this, it is necessary to have a realisticview of how hymenachne impacts onoverall property management.

Planning takes place at a number of levels,including:

• paddock to property level• local government level—through the

development of local government pest management plans

• catchment level• regional level—through regional strategy

groups.

To create a greater sense of involvement, itis helpful to involve others who are directlyaffected by hymenachne.

On a property level, a successful plancannot be developed in isolation from otherproperty operations and must be integratedinto the overall property management plan.The management principles suggested herefor control and local eradication ofhymenachne can be applied to other weedson a property and, ideally, strategies formanagement of all weeds should beincluded in a single plan. It isrecommended that a weed control planshould have at least a 5–10 year time frameand be reviewed annually.

A range of planning processes can beadopted to develop a weed control plan.The following suggested control anderadication plan has six steps.

Step 1: Identify and prioritise problem areas• The easiest way to identify problem

areas is by using a map of the property. This can be a satellite image, aerial photograph or hand-drawn map. The more accurate and current it is, the easier it will be to accurately calculate control costs and to track the long-term effectiveness of control programs.

• Use separate transparent overlays when developing maps—one to indicate property improvements, one for vegetation types and natural features, and another devoted solely to weed infestations. Using different overlays can make each section of the map easier to interpret and can also be helpful when making management decisions (e.g. determining the best place to put fences).

• On the map, outline all natural features, improvements and property boundaries; then indicate areas of hymenachne (and other weeds), noting the size and density of each infestation.

• Prioritise the areas for control or eradication at the property level and at a paddock-by-paddock level, keeping in mind features outside the property such as seed sources, seed and plant dispersal routes and vulnerable areas.

• When confronted by large infestations, it may be better to control small, isolated outbreaks before managing the main infestation.

• Consider the legal and ethical responsibilities you have (e.g. the threat from hymenachne to neighbouring properties).

• Consider relevant local government, catchment or regional priorities and plans.

• To prevent infestations from spreading, focus initial control efforts on isolated outbreaks. A good rule of thumb is to start with the section that will be easiest to control and then gradually work towards the thicker patches. In the case of hymenachne, start work in the upper catchment to prevent reinfestation lower down.

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� Focus initial control efforts on small isolated outbreaks

� Identify what resources are availablefor control

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Step 2: Determine the control options

• With a range of methods available for hymenachne control, decide which will be most appropriate in the given situation. It may be necessary to use a combination of methods to complete the job effectively.

• Identify what resources are already available or affordable, such as spray equipment, machinery and labour. This will indicate which control methods will be the most economical and beneficial.

• Decide which methods will be required at all phases of the program—initial control, follow-up and ongoing monitoring. If unsure about control methods, contact local government pest management officers for further advice.

Step 3: Develop a financial plan• Estimate the cost of the management

strategies and control options.• Evaluate the costs of the chosen

methods in relation to those of other operations currently occurring on the property to ensure that they are economically viable.

• Integrate these costs into short-term and long-term property budgets.

• Find out if there are any financial incentives available to assist with control programs.

• Consider all costs (including the hourly running costs of machinery and labour). If necessary, seek advice from local government or departmental weeds officers before committing a large amount of money.

• Take into account the cost of future control—this is frequently underestimated.

Step 4: Schedule activities• Consider how effective various control

methods will be at different times of the year and compare this with the time available for carrying them out.

• Try to integrate weed control with other property management activities (e.g. combining a routine burn with the control of hymenachne).

• Schedule all weed control activities for the year.

• Make hymenachne control a regular part of property management. When developing a plan, allow for monitoring and follow-up after the initial treatment, and ensure that follow-up occurs within three months.

� Decide on the most appropriate method of control in the given situation

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Step 5: Monitor progress• Monitoring should be an integral part

of any control program. It can be used to check how well a treatment worked, to identify areas of regrowth and to find out where follow-up is required.

• Use the property map as a record of the problem before any control work has commenced.

• On the map, show any new or previously treated areas of infestation.

• Use photograph reference points to record progress. Photographs should be taken from the same location each time treatment or monitoring is carried out.

• Document control costs and resource requirements.

• Incorporate monitoring activities into the yearly timetable.

Step 6: Follow up what was started• As no control methods for hymenachne

result in 100% kill and because some seed germination and regrowth is likely, follow-up is crucial.

• From the monitoring sites, identify areas where follow-up is needed.

Helpful tips• As there is no ‘quick-fix’ for weed

control, developing a management plan and committing to it are essential for the long-term effectiveness of your efforts.

• Any control plan is useless without implementation. If (because of the size of the problem or lack of experience) it is difficult to start planning, seek professional advice or start planning on a smaller scale.

• While the plan must be structured, it should be flexible enough to allow for changes brought about by uncontrollable external influences such as drought, floods or fluctuating commodity prices.

The plan must be reviewed annually toassess the effectiveness and efficiency of thecontrol options and strategies implemented.

Landholders can design individual propertymanagement plans in conjunction with theirlocal government pest management officer.Such plans can include strategies to controlthe weeds, including buffer zones,containment lines and time frames in whichthe actions are to be carried out. This maybe done in line with their local governmentarea pest management plan.

For example, the Burdekin Shire Council inNorth Queensland has drawn up a numberof pest management agreements forparticular areas of the shire. The agreementis a formal contract between the landholderand shire council covering certain aspects of the management of wetlands or lagoons.This stipulates an equal share basis for

23

ongoing maintenance program costs and atime frame for the maintenance period. Theareas specified in the agreements are generally areas adjacent to landholders’properties that have previously been treated.

An example of this is Horseshoe Lagoon,which is featured as a case study on page 56 of this manual. While the majorityof these weeds have now been controlled atthis site, the owners of adjacent land mustcontinue to control weeds and maintainthese wetlands.

The landholder‘s legal responsibility isacknowledged under the Land ProtectionAct 2002. An example of such anagreement between council and landholdercan be viewed in the Appendix.

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� Areas such as Horseshoe Lagoon will be maintained under local pest management agreements

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Prevention of spreadThe most cost-effective way of dealing withany weed is to prevent its introduction.Preventing the spread of hymenachne intocatchments at risk of infestation should be a management priority. This prevention ismade extremely difficult when hymenachnegrows in pastures in the upper catchment,because spread by water flowingdownstream can easily occur. As a generalrule, upstream infestations should be treatedfirst. Hymenachne control requires a policyof regular catchment monitoring, and theability to eliminate any small infestations.

The clearing of native riparian vegetation,combined with increased soil and nutrientrun-off from crop land—especially landused to grow sugar cane and bananas—creates an ideal habitat for a range of exoticgrasses including hymenachne. Improvedfertiliser and cultivation practices incropping areas will reduce nutrient andsediment run-off.

Good hygiene practices prevent the spreadof hymenachne on machinery, boats, trailersor motor vehicles. Cattle grazing onhymenachne pastures reduces biomass, butcan also lead to further spread. Seeds andplant material can be transported on theirhooves, or be digested and depositedelsewhere. Graziers must be aware of thispotential spread and take appropriate actionto avoid it. Water birds, which may spreadhymenachne seed between catchments,cannot easily be managed.

Greater public awareness of the threatposed by hymenachne, the importance of itscontrol and ways to minimise its spread willcontribute to the prevention of spread ofhymenachne.

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S e c t i o n 3

� Cattle can spread hymenachne

� Field days raise public awareness of thethreat of hymenachne and provideinformation about control

� Water birds can spread hymenachne between catchments

Toolbox for hymenachne control

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Choosing controlmethodsEffective control strategies for hymenachneare limited. There are significantenvironmental concerns and restrictionsassociated with the use of herbicides inaquatic environments. Human alterations to hydrology, including pondage andmodifications to waterways, can compoundthe difficulties in hymenachne control dueto increased nutrient availability.

While hymenachne populations are low,early detection and rapid response effortsincrease the likelihood that control andmanagement will be successful. Oncediscovered, eradication or containment ofnewly detected infestations is a key priority,as this is more likely to result in significantlong-term savings than if weeds are allowedto proliferate.

When choosing control methods, the bestapproach is usually to combine differentmethods to suit the particular situation.Control may include chemical, mechanical,and fire, combined with appropriate landmanagement practices.

Climate can influence the type of controlundertaken. In the wet tropics ofQueensland, there is a greater reliance onchemical control, as many of the areasinfested with hymenachne do not dry outsufficiently to use other control methods. In the dry tropics, hymenachne can bemanaged through a combination ofmethods, which include land managementpractices such as grazing.

Mechanical controlmethodsMechanical or physical removal will notcompletely eradicate hymenachne becauseof its ability to reproduce vegetatively fromvery small pieces. Mechanical harvesting to remove hymenachne and other weedshas occurred in the Burdekin Shire in NorthQueensland, but this requires ongoingcontrol on a monthly basis. A number ofQueensland councils have now acquiredweed harvesters to regularly treat theiraquatic weeds.

The success of any harvesting operationdepends on the prompt and completeremoval of all cut weeds. Haphazard orpartial removal can increase the problem,since each remaining plant fragment has the potential to form a new weed colony.Cut plants left in the water will decay and release nutrients. This decompositionprocess uses oxygen, which can result in fish kills.

Weed harvesters are more effective onfloating waterweeds such as water hyacinth(Eichhornia crassipes) and salvinia (Salviniamolesta) and using only this method toremove hymenachne is not cost effective.Weed harvesters can be useful in removingimpenetrable floating weed mats ofhymenachne from deeper water bodieswhere access is otherwise difficult.Harvesting of weeds provides immediaterelief from unwanted plant growth and doesnot endanger fish life.

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Another mechanical method for controllinghymenachne is the use of a weed rake. TheNorth Burdekin and South Burdekin waterboards in North Queensland employ weedrakes to clean weeds from irrigationchannels.

The weed rake consists of heavy-duty steeltines mounted on the end of an excavator.The rake is more effective than a bucket, as no additional soil is removed from thechannel. As demonstrated in the photo, theweed rake extends into the water and pullsall the vegetation to the bank. Oncedeposited on the bank, the weeds can bemoved or sprayed. This method can removelarge mats of hymenachne from thechannels in a relatively short period of time.This method of weed removal can be usedas part of an integrated approach in thecontrol of hymenachne and para grass.

However, as with weed harvesters, it islikely that plant pieces will break off duringthis operation and reinfest the channelbanks. To minimise reinfestation ofchannels, hymenachne should be movedaway from the shoreline and above theflood level.

Land managementThe control of hymenachne through landmanagement practices is often achievedthrough a combination of methods. Forinstance, grazing alone will not provideeffective control but a combination ofgrazing and fire, followed by flooding, caneliminate hymenachne from many areas.The following pages outline some of theland management actions that can assist inthe control of hymenachne.

Manipulating water levels• Flooding can offer some control of

hymenachne when the above-ground vegetation has been removed, as it is difficult for hymenachne to keep up with rising water levels. Hymenachne can ‘drown’ when inundated with water, especially after being grazed down low, burnt, or reduced in height with a slasher. Any regrowth that is not killed will be weakened and is more susceptible to follow-up with herbicides.

• Drying, or lowering water levels, may offer some extent of hymenachne control. This practice is common in the United States of America, in ponds where drawdown occurs in the winter

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� Weed rakes are useful to clear hymenachne and para grass from irrigation channels

� Burdekin shire weed harvester

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months to expose weeds to harsh conditions including desiccation (drying out) and freezing (Helfrich et al. 2000). Vegetation exposed by lowering water levels should be removed, or rotting plants will contribute nutrients that promote new growth when the water level is raised. Hymenachne does not tolerate dry sites, but little research has been done on drawdown as a control method for aquatic weeds in Australia.

Grazing In many coastal regions of NorthQueensland, reduced grazing—due toincreased cropping—has resulted in theexpansion of exotic grasses in manyriparian and wetland habitats.

Controlled grazing represents a viablemeans of broadacre control of hymenachnein wetland and riparian zones of the drytropics. Many of these wetlands areseasonally inundated, but dry outsufficiently in the dry season to allow cattlegrazing. Grazing in the Wet Tropics isusually not an available control option, aswetlands do not dry out.

Some of the worst hymenachne infestationsin the dry tropics occur in areas where thehydrology has been artificially modified byregulated flows, irrigation and damming.There is a strong relationship betweenhydrology and grazing hymenachne:

• Deep water provides a grazing refuge for floating mats of hymenachne.

• Sufficient dry season drawdown of wetland water levels means that hymenachne can be grazed down to very low levels.

• Drying out allows fire to be used as a complementary management tool.

• Rapid rising of water levels within a wetland basin with grazed down hymenachne margins can drown residual plants.

A number of grazing and burning trials arebeing conducted by Wetland Care Australiain the lower Burdekin area of NorthQueensland. These trials are also trying to ascertain the impacts of other aspectsassociated with grazing such as erosion,trampling risks, the merits of different stocktypes, appropriate grazing regimes, andrecruitment of native vegetation.

Grazing in riparian zones can have manynegative impacts, including reduced waterquality due to increased nutrient loading—primarily from urine and manure—andincreased turbidity due to bottom sedimentdisturbance and bank erosion.

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� Grazing provides temporary control ofhymenachne

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Riparian grazing can also be beneficial, as it allows the removal of weed biomass andassociated organic (nutrient) loading. It alsocreates open areas of water, which aids inoxygenation of the water column.

Where damage to banks is minimal, the positive aspects of grazing seem tooutweigh the detrimental aspects. This can be seen in areas such as the Burdekinfloodplain.

Grazing alone in coastal areas will not killhymenachne, which is noted for its abilityto withstand heavy grazing. While cattlecan reduce the amount of hymenachne,they can also potentially spread plantsegments or seed in their hooves or in mudattached to their bodies. An added risk isthat hymenachne seed eaten by cattle canpass through the gut and germinate. Cattleshould therefore be kept away from cleanareas for several days after grazing onflowering hymenachne, to prevent furtherweed spread.

Dry conditions, combined with heavygrazing, have eliminated hymenachne fromponded pastures in some inland areas of theAtherton Tablelands in North Queensland (J Kernot 2005, pers. comm., December).

A research project by CSIRO andQueensland Parks and Wildlife is exploringthe use of fire and grazing to control paragrass in the Townsville Town CommonConservation Park. The team of scientists isexamining how grazing and fire can reducethe abundance of para grass. The trial isbeing conducted over 72 hectares and fourdifferent treatments are being compared.

While work did not start on this projectuntil 2004 and results are not yetconclusive, initial findings suggest thatgrazing, in combination with fire, is themost effective method of reducing paragrass in this situation.

The project also looks at the changes inwetland vegetation and animal communitiesfollowing the different treatments. Theinformation gathered from this project willbe used to develop and promote methods torestore other coastal wetlands degraded bypara grass. Despite the differences betweenpara grass and hymenachne—most notably,that hymenachne is able to grow in deeperwater—some recommendations may haveapplication for the management ofhymenachne in wetlands.

ShadingSolar sheeting or solarisation—coveringinfestations with dark plastic—can kill smalloutbreaks of hymenachne. Shading by tallvegetation has also been investigated as ameans of reducing the amount of plantmaterial infesting rivers and creeks. This canoffer long-term, cost-effective weed controland is considered more ecologically soundthan chemical or mechanical forms ofcontrol. However, tall vegetation is notlikely to become established in theseasonally inundated floodplains, andwould also have its own impacts on such systems.

Shading has been investigated as a means of controlling para grass. In a studyconducted in North Queensland, thebiomass and height of para grass were

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substantially decreased following threemonths under 90% shade (Bunn et al.1998). Such data suggest that the restorationof tall native riparian vegetation can providelong-term means of controlling invasivegrasses.

In the United States, shading has beentrialled on water bodies by using blackplastic sheeting attached to Styrofoam™floats. These floating shades can be movedeasily to different places for spot treatmentof waterweeds. The black plastic raft mustremain in place for at least one month to be effective (Helfrich et al. 2000).

A shading trial is currently being conductedby NRMW at Euramo, near Tully in NorthQueensland, to ascertain the impact ofshading on hymenachne. The trial site isusing artificial shade (from shade cloth) andnatural shade (from vegetation) to comparethis method of control with chemicalcontrol of hymenachne. Recordings fromthis trial include biomass samples and soilseed bank samples. The trial is beingmonitored annually.

FireFire can be used as an additional, cost-effective means of reducing stands ofhymenachne. Burning can generally only be done during the dry season when plantshave dried out sufficiently to providesuitable fuel. Great care should be takenwith fire, as hymenachne can create largefuel loads that promote intense, hot firesthat can destroy native riparian vegetation.Reduced tree canopies following hot firescan actually promote grass growth andincrease fuel levels. Fire in pure stands of hymenachne can be useful for reducingstands and may be followed up by grazing,herbicides or flooding.

Fire has been successfully used inconjunction with grazing and herbicides. In the lower Burdekin, fire is followed bygrazing, just prior to the wet season. In theNorthern Territory, fire was successfully usedafter herbicide application to reduce thebulk of hymenachne to a more manageablelevel. For more information, see the casestudy of Lambells Lagoon on page 48 of this manual.

Fire will destroy seed on the soil surface but will not destroy buried seed. The heat ofthe fire may even stimulate buried seed togerminate and the resulting seedlings wouldneed to be treated by herbicide or grazing.

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� Fire can be a useful tool in the control ofhymenachne and para grass

� Hymenachne seedlings after fire

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Biological controlBiological control of hymenachne iscurrently not available in Australia. Anybiological control agent for hymenachnewould need to be specific for Olivehymenachne. This would ensure that thereare no impacts on the native hymenachne,other grasses, or the unrelated buteconomically important sugar cane. To finda biological agent that will only attackexotic hymenachne will requireconsiderable research into the pestsassociated with both hymenachne species.

In Florida in 2000, severe damage causedby an unknown insect was noted onhymenachne plants. This insect was lateridentified as the blissid bug (Ischnodemusvariegatus). This bug is known to occurnaturally in South America but was notpreviously recorded in Florida (Brambila &Santana 2004). The bug appears to feed andbreed only on Hymenachne amplexicaulis,but further host-range testing is requiredbefore this is considered an option inAustralia.

Aquatic weeds andherbicidesMost herbicides are not registered for use inaquatic situations and their labels carry onlygeneral instructions to avoid contaminationof watercourses. It is not always clearwhether these products should be used onland adjoining water bodies and, if so, howfar from the water they should be used.

Chemical labels must be read carefully andcompletely, as it is illegal to disregard labelprohibitions. The risk of water becomingcontaminated with herbicide, and theeffects of herbicide on non-target organismscan be affected by:

• the amount of herbicide applied• the method of application• how mobile the herbicide is (in soil

and water)• the persistence of the herbicide• the toxicity of the herbicide to flora

and fauna• weather conditions at the time of,

or after, application.

Movement of herbicides into aquaticsystems is possible via direct spray, vapourdrift, surface run-off, movement of soil ormovement into groundwater. This usuallyinvolves only a very small percentage of theherbicides originally applied, though thiscan be significant if the total amount beingused in the catchment is large. Alsoconsider that currents may carry herbicidesdownstream, where they can affect otherecosystems, landholders and water users.

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� Ischnodemus variegatus, a potential biological control agent

� Damage to hymenachne by the blissid bug (Ischnodemus variegatus)

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When herbicides are applied in or nearwatercourses, the distance the herbicideneeds to move—by spray drift or run-off—to reach water is much shorter. Small risesin water level can also result in the treatedland being flooded. Such short-distancemovement is difficult to predict, as it isinfluenced by weather conditions and theskill of the operator. Although the amount of herbicides used for aquatic situations isusually very small, the input of suchherbicide use can still be an importantsource of contamination.

Indirect impacts of weed control byherbicides are more likely if the weedmakes up a large component of the aquaticvegetation. Such impacts include erosion ofbare banks, an increase in watertemperatures after shade is removed, andthe fouling of water by rotting aquaticweeds. These indirect effects can beminimised by removing weeds gradually, inconjunction with restoration of banks andbare areas.

Chemical controlmethodsHerbicides are an important component of integrated weed control. The advantagesof using chemicals for the control ofhymenachne are their flexibility, the speedof treatment and the relatively low cost.Many coastal councils in Queensland havereported that the initial expense ofcontrolling hymenachne by chemical meanscan be high due to the widespreadproblem, but these costs reducedramatically during the follow-up andmonitoring stages.

Safeguards and label informationIn Australia, the Australian Pesticides andVeterinary Medicines Authority (APVMA)regulate the use of pesticides, includingherbicides. Chemical products are assessedfor toxicity, efficacy, environmental impact,residues, and any implications foroccupational health and safety. By law,herbicides must only be used in accordancewith label instructions or off-label permits.

Personal protective equipment—such asprotective clothing, eye protection andrespiratory protection—must be used, also in accordance with manufacturers’recommendations.

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� In aquatic situations, try to minimise the amount of herbicide entering water

� Care must be taken when applying herbicide next to watercourses

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Herbicides must be treated with great care.Before use:

• ensure all permit conditions are met• read the instructions and conditions for

use on the label, specifically critical comments for use in aquatic areas

• consider the possible impact on non-target vegetation and the surrounding environment.

All methods of chemical control mustcomply with the relevant state and localgovernment native vegetation legislation.Causing even accidental death of nativevegetation could be a breach of thislegislation.

PermitsThere are several herbicides used inQueensland to control hymenachne andapproved for use under off-label minor usepermits. Except for herbicides authorisedunder these permits, no products areregistered for the control of hymenachne.

Off-label permits, issued by the APVMA,stipulate a number of requirementsincluding who can use the permit, whichchemicals can be used, how the chemical can be applied and any additionalconditions. Permits are in force for aspecific period and cannot be used oncethis period expires.

There are currently four valid permits for the control of hymenachne in Australia, allof which are in Queensland. Some permitscan only be used in certain locations bycertain persons. A condition of all permits isthat the person intending to use the permitmust read, or have read to them, the detailsand conditions of the permit.

PER7485 allows the use of glyphosate forcontrol of hymenachne in aquatic situationsThis permit also allows the use of Arsenal® 250, Fusilade™ and Verdict* for thecontrol of annual and perennial grasses, butthe rates stipulated in the permit are too lowfor effective control of hymenachne andcannot be used close to waterways (J Vitelli2005, pers. comm., December).

PER6961 allows the use of glyphosate forthe control of hymenachne in the Mareebaarea.

PER7039 contains other conditionsincluding the monitoring and collecting of water samples that have to be submittedfor testing of pH, dissolved oxygen andconductivity. Upon completion of themonitoring program, a report stating theeffectiveness of the herbicide onhymenachne, as well as the results of allwater testing, must be submitted to theAPVMA.

PER9076 prescribes certain conditions foruse, including monitoring prior to and afterapplication at four representative sites. Thisincludes the collection of water samplesthat must be submitted for testing of pH,dissolved oxygen and conductivity.

The above permits all apply to applicationby knapsack, handgun or boom spray. Therestrictive nature of the permits may meanthat a number of landholders cannot legallyuse any chemical for control ofhymenachne. If, as a landholder, youcannot control hymenachne under any ofthe permits described, you can apply for aminor use permit in conjunction with thelocal shire.

* Trademark of Dow AgroSciences LLC

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Table 1: Current off-label minor use permits for hymenachne control

Permit Products/chemicals Rate Users/situationsNon-crop Areas

PER7485

Effective 1 July 2004 to30 June 2009

PER6961

Effective 24 September2003 to 30 September2008

PER7039

Effective 19 July 2004 to 30 June 2009

PER9076

Effective 19 January2006 to 28 February2007

Roundup® Biactive™,Weedmaster® Duo

(360 g/L glyphosate)

This permit covers anumber of herbicides butthe herbicides above arethe only ones to be usedin aquatic situations.

Roundup® Biactive™

(360 g/L glyphosate)

Verdict* 520

(502 g/L haloxyfop)

Verdict* 520

(502 g/L haloxyfop)

1 L/100 Lwater or 10L/ha deliveredvia boom

Max. 14 L/ha

770 mL/hadelivered viaknapsack,handgun orboom sprayonly

770 mL/hadelivered viaknapsack,handgun orboom sprayonly

Pest control operators; employees of,or supervised by local/stategovernments; members ofenvironmental groups e.g. Bush Care,Catchment Care.

Spot spray in aquatic and wetlandareas.

Permit is not restricted to any area inQueensland.

Persons generally.

For use in drainage reserves(Mareeba–Dimbulah Water SupplyScheme only).

Restricted to trained staff of MackayCity Council, Mackay CaneProtection and Productivity Boardand research staff of the Departmentof Natural Resources, Mines andWater.

Ponded and non-flowing drainageareas and banks of flowing waterways(Mackay Shire only).

Restricted to trained employees of theCardwell Shire Council.

Ponded and non-flowing drainageareas and banks of flowing waterways(Cardwell Shire only).

All current permits can be viewed on the APVMA website at <www.apvma.gov.au>.* Trademark of Dow AgroSciences LLC

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For other states, refer to the localgovernment pest management officer or to the state agricultural or primary industriesdepartment (see Contacts on page 65).

In the past, local governments and otherorganisations have obtained permits for theuse of helicopter application of herbicidesto control hymenachne. Aerial applicationcan be very effective where large areas ofhymenachne occur or are difficult tocontrol due to deep water or limited access.Controlling hymenachne by the aerialspraying of glyphosate has been successfulin the Burdekin region of Queensland,where this weed has been controlled inseveral lagoons. The remaining hymenachnealong the edges of the lagoons could thenbe controlled by chemical applicationsfrom knapsacks and handguns.

When to sprayCorrectly timing chemical control canreduce seed production. Flowering trialsconducted by NRMW in Charters Towersindicate that hymenachne flowering occursonce the day length drops below 12 hours. Controlling hymenachne betweenSeptember and March in the Queenslandtropics may reduce the number of newseeds entering the seed bank.

Effective control of hymenachne using foliarapplication depends on several importantfactors:

• Plants must be actively growing—avoid spraying when the plant is stressed.

• Plants must be sprayed to the point of run-off, wetting every leaf. Do not spray past the point of run-off.

• Spray may drift onto wetlands, natural surface waters, soil, neighbouring properties or other sensitive areas—always check weather conditions before spraying.

• Appropriate spraying equipment must be used to prevent chemical drift.

• Rain will cause herbicide run-off and reduce its effectiveness—check weather reports and do not spray if rain is expected within 48 hours after spraying.

• Treatments must be monitored and followed up.

� Special permits are required for aerialapplication of herbicides

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Glyphosate is the main chemical used to control hymenachne; however, itseffectiveness may be variable and could beonly 50%. It is therefore very important thatall sites are revisited and treated every threemonths. Aerial chemical applicationrequires repeated treatments every eightweeks to control seedling germinationduring the early stages of the treatmentprogram.

It is a condition of the ‘minor off-label use’permit to notify the APVMA of any incidentsof off-target contamination or damageassociated with the foliar application ofherbicides.

The cost of hymenachne control depends onthe extent of the infestation, the controlmethods used and the degree of difficulty ingetting spray equipment to infestations (siteaccess).

Monitoring andevaluationAlthough the above methods to controlhymenachne can achieve good results inthe right situation, there is always a need for monitoring and follow-up treatment.Monitoring is an essential part of any weedcontrol project. Sometimes plants aremissed, errors in mixing or applyingchemicals occur, or other unforeseen factorsreduce the overall kill achieved. Somecontrol methods, such as mechanicalcontrol, can also contribute to furtherinfestations downstream.

Hymenachne sites should be revisited everythree months. Returning to the site afterinitial control or follow-up work will detectany seedling establishment and identifyplants that received inadequate spraycoverage. All surviving and new plantsrequire follow-up treatment to prevent themreaching maturity.

It is recommended that monitoring continuefor a minimum of five years. Monitoring andregular follow-up over a longer period willresult in more effective control. Carefulmanagement of funds is required to enablea monitoring and follow-up program to be implemented.

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� Regular monitoring will identify areas ofseedling establishment

� Riverbanks infested by hymenachne may be prone to erosion after hymenachne is controlled

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Where seedlings or juveniles of nativevegetation are present within a hymenachneinfestation, replanting or reseeding may notbe required. In these areas, the removal of hymenachne can result in successful re-establishment of native vegetationthrough natural means. It is thereforeimportant that the control methodsemployed have minimal impact on thenative vegetation. Immediate control ofhymenachne is imperative in these areas to prevent the native vegetation from beingoutcompeted.

Where sites are prone to erosion or furtherweed establishment after initial treatment,replanting using local native plant stock willassist recovery. This is particularly importantalong drainage lines and in agriculturalareas where hymenachne may have beenretained to reduce soil erosion.

Research into chemicalcontrol methods forhymenachneIn Queensland, only 12 herbicides areregistered for the control of 226 weeds thatgrow in or near aquatic areas (Vitelli,Madigan & Ruddle 2005). Due to thecomplexity of herbicide applications onaquatic weeds, the APVMA is reluctant toregister any more herbicides until researchdata can prove that there are no detrimentaleffects to other aquatic organisms. Researchtrials have identified a number of effectiveherbicides for use on hymenachne, but mostare unsuitable for aquatic situations.

Field experiments to determine the effect of foliar-applied herbicides on hymenachnewere conducted by staff from the thenQueensland Department of NaturalResources between 1997 and 2000.Experimental sites were chosen for theirdense and uniform monocultures ofhymenachne. At each site, all plants weresprayed to the point of run-off.

Initial trials indicated five effectiveherbicides and further trials were conductedto determine the lowest effective ratenecessary for control of hymenachne.Parameters to determine herbicideeffectiveness included mortality, biomassreduction, biomass regrowth and resprayvolume. Based on these parameters, themost effective herbicides were Verdict*(haloxyfop), followed by Fusilade™

(fluazifop), Arsenal® (imazapyr), Velpar®

(hexazinone) and Roundup® Biactive™.

* Trademark of Dow AgroSciences LLC

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� Researchers hope to find better herbicides for the control of hymenachne through pot trials

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Velpar and Arsenal are broad-spectrumherbicides and pose problems to off-targetvegetation. Their application in naturalwetlands would damage and kill nativeplants and could facilitate reinvasion oftreated sites by hymenachne or otheropportunistic plants. Velpar in particular hasalso been noted for its mobility in soil afterapplication and, following rainfall, canmove into surrounding non-target areas.

Other research into the effect of Verdict 520herbicide (haloxyfop) in aquatic situations isnearing completion. Research identifiedVerdict 520 as one of the most effectiveherbicides for controlling hymenachne, buta major difficulty in registering haloxyfop isthe lack of information available to decisionmakers about its effect on aquatic life.

A laboratory-based haloxyfop studyindicated chemical presence in all aquaticspecies tested, but levels were low and noorganism deaths were attributed toherbicide toxicity. Under field conditions,herbicide concentrations were lower than inthe controlled environment and currentfield studies in three North Queensland sitesshould validate and further quantify residuelevels. Data from such research willcontribute to the registration of haloxyfopand assist in establishing withholdingperiods for this product.

ConclusionDespite the range of control methodsoutlined above, the eradication ofhymenachne from northern Australia is not considered feasible due to the plant’sresilience, its extensive distribution, the lackof effective chemical control options, andthe reluctance of graziers to destroy avaluable pasture. Through carefully plannedcontrol and management activities, workingin conjunction with neighbours and acrosscatchments, hymenachne can be containedand its impacts can be minimised.

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� Field-based trials will allow researchers to assess the effectiveness of herbicides on hymenachne

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� Hymenachne can invade water storage areas

� Hymenachne can out-compete native vegetation

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� Always try to control hymenachne before flowering and seed set

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The following case studies highlight theproblem of hymenachne in both Queenslandand the Northern Territory. They includeaccounts of various control methods and thesuccesses and challenges faced in differentsituations.

One case study features a research projectwith some surprising findings about theimpact of hymenachne control in aquaticareas. It contains essential information forall land managers who control hymenachnealong waterways.

The need for strong collaboration betweenvarious sectors of the community andgovernment, especially when large infestedareas require control, is highlighted in twoof the case studies. Early intervention andpersistence in controlling hymenachne hasreduced the weed to a manageable level fora grower and a North Queensland council.

The case studies also emphasise the need to integrate the various control options tomanage hymenachne.

A case study with a grazier explains theimportance of hymenachne to the cattleindustry, especially in the drier regions of northern Australia. Control ofhymenachne in these areas could have amajor impact on the profitability of cattleproduction.

The case studies are the result ofconsultation with people who have beenclosely involved with hymenachne and whohave generously donated their time andphotographs for this publication.

Early intervention has reduced thehymenachne problemin the Cairns region

BackgroundHymenachne in the shire of Cairns isbelieved to be the result of planting done by landholders in the 1990s. The plantspread from grazing lands into wet areas,including drains and creeks, and was alsofound along the major rivers and tributariesof the region. Hymenachne increasedrapidly in both distribution and density inthe Cairns region.

After numerous sightings of the weed, theCairns City Council declared hymenachne a noxious weed in 2000 under the LocalGovernment Act 1993. At this time,hymenachne was still being promoted andseed was commercially available. Althoughhymenachne was only beginning to berecognised as a pest, immediate

Case studies

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S e c t i o n 4

management was essential, as the benefitsof control at this early stage would preventany costs associated with futuremanagement.

Controlling hymenachneInitial control of hymenachne was done by council staff, in cooperation with locallandholders who had infestations on theirland. All the hymenachne in the Cairnsregion was controlled by chemical means,including Arsenal® and glyphosate.Glyphosate was the only chemical thatcould be used in wet areas and alongwaterways. Council staff found that whileglyphosate provided some control, it wasnot very effective on thick mats ofhymenachne, as the chemical did notpenetrate and control the bottom layers ofthe weed. Poor chemical control requiredmany follow-up applications.

Many of the hymenachne infestations werenot accessible from land and had to bereached by boat. Cairns City Council stafffrequently used canoes, punts or small boatsto access the weed from the river. Theseoperations required good boating skills, as it was often difficult to manoeuvre the boatin running water. Most of the spraying wascarried out during the dry season, but weedcontrol also occurred during the wettermonths where site access was possible.

Funding from National Heritage Trustobtained in 2001 was used to controlhymenachne along the Wyvuri swampesplanade of Frenchmans Creek in Babinda.The funding was also used to survey andmap this region.

Cairns City Council has received no otherfunding for the control of hymenachne butcontinues to control this weed as part oftheir pest control program. This includescontinually monitoring the areas alreadysprayed, and surveying and controllingfurther infestations. Monitoring activitiesinclude travelling the full length of the mainrivers at least twice per year to look forfurther infestations of hymenachne.

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� Hymenachne in the Cairns region was spread by seed and vegetative parts

� Many hymenachne infestations could onlybe accessed by boat

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ObstaclesIn 2000 and 2001, landholders in theCairns region continued planting ofhymenachne, which further increased thespread of the weed. Many landholders didnot control hymenachne on their propertiesunless the weed impacted on their farmingenterprises, such as by invading cane land.While the council controlled hymenachnefrom esplanades along rivers, landholderswith river access did not practise weedcontrol and hymenachne reinvadedpreviously controlled sites.

Flooding of rivers and creeks in the wetseason contributed to the spread ofhymenachne. While floodwaters washedsome hymenachne out to sea, where itperished, flooding also led to newinfestations in low-lying areas. Access to many of these areas remains difficult,except by boat.

Despite the obstacles, the council believedthat they had much of this weed undercontrol by early 2005. However, infestationsfound in areas not subject to floodingsuggested further spread of hymenachne by waterfowl. Weed dissemination by birdsis highly unpredictable and makes themapping of hymenachne much moredifficult.

The longevity of the seed also means thatfollow-up control must continue for anextended time period. The current chemicalcontrol options remain limited and requirecontinued follow-up applications to controlhymenachne.

Public awarenessA large public meeting about hymenachneinfestations in the Mulgrave River systemwas held in 2005, to raise greater awarenessof the problem among landholders and thepublic. The Mulgrave River near Gordonvalehas numerous islands that have createdmany smaller streams, each of which couldpotentially contain hymenachne. If leftunchecked and untreated, the weed could‘choke’ the river system by growing acrossthe whole of the river. The public meetingalso served to facilitate right of accessthrough private properties adjacent to theriver for the purpose of weed control.

Containment and managementNew infestations are still being found, but the Cairns City Council has a goodknowledge of where the weed occurs andhas the experience to manage and containinfestations. There is significantly lesshymenachne in this shire than in othershires in the Wet Tropics regions of NorthQueensland. This can be attributed to earlyintervention and continual survey andcontrol. While the council does not believethat they will completely eradicate thisweed, they are successfully managinghymenachne in the Cairns region.

� If left unchecked and untreated, hymenachnecould ‘choke’ the river system

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Canegrower has spent thousands onhymenachne control

BackgroundIn 1985, Nick Stipis bought his first sugarcane farm near Euramo, a small townsituated in the Cardwell Shire on the coastof North Queensland. Between 1989 and1994, he bought four cattle properties in the Murray Upper area to expand hiscanegrowing enterprise. These cattleproperties contained hymenachne innumerous low spots where it had survivedduring drier years. All of Nick’s farms aresituated on the Tully–Murray floodplain, an area between the Tully and Murray rivers prone to severe flooding during verywet years.

Nick first found hymenachne in his sugarcane in 1998. He was not familiar with thespecies and he called on the Tully CaneProductivity Services for plant identification.This organisation frequently helps growerswith pest and weed problems in cane, butthey did not recognise the grass either. Theplant was finally identified by localgovernment officers as Hymenachneamplexicaulis.

The Cardwell Shire Council not only knewof this weed, but had been concerned aboutit since 1993. They first found it in theMurray Upper region while this area wasbeing opened up for cane production.Hymenachne had been extensively plantedby graziers in the late 1980s, but much ofthe grass had not survived the dry yearsfollowing planting. However, hymenachneflourished in low-lying areas, lagoons anddrains and was being spread further byfloods and waterfowl. The Cardwell ShireCouncil estimates that some 3000 hectaresare currently infested by hymenachne in theregion.

Impact of hymenachne Nick observed the aggressive nature ofhymenachne first-hand when it was foundgrowing in one of his sugarcane crops.Hymenachne can grow faster and tallerthan cane, and will decrease productivitythrough direct competition. Hymenachneeven persisted between cane rows in lowlight intensity. When not competing withcane, it was able to set seed and spreadfurther into the paddock.

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One 4.5 hectare paddock of cane was sobadly contaminated by the hymenachnethat Nick did not send this cane to the sugarmill. Instead, the area was burnt in anattempt to rid the paddock of hymenachne.Burning was followed by slashing, aerialand on-ground herbicide spraying, andcultivation. The paddock was left fallow forfour years to eliminate all hymenachne fromthe block. Nick was not prepared to replantcane in an area that contained anyhymenachne. The cost of controllinghymenachne and the resulting loss ofincome from this block cost Nick in excessof $30 000.

Control measures and costWhile Nick does most of the weed controlon his land, he has also been assisted byCardwell Shire Council staff. The councilsupplied him with herbicides, as well asequipment such as a Quikspray® unit.

Nick has removed hymenachne by bothchemical and manual means. He oftenremoves seed heads manually and marks

the remaining plant for follow-up. Isolatedhymenachne plants have frequently beendug out of cane paddocks. Nick has alsoclosed in a number of drains on hisproperties to prevent the spread ofhymenachne via these drains. He has evengone to dangerous lengths to manuallyremove hymenachne from the bottom ofwetlands—using a rope for a quick escapefrom lagoon-dwelling crocodiles.

Nick uses the herbicide Fusilade™ onhymenachne in all non-aquatic areas. He has found this to be the most effectivechemical for hymenachne control, and iswilling to pay the extra cost for thisherbicide to achieve a good kill. He addscanola oil to the herbicide for betterchemical absorption. Nick has also used theherbicide Gramoxone® to burn off the seedheads of hymenachne.

The Cardwell Shire Council used Verdict*(with Uptake* or canola oil) for the controlof hymenachne in all aquatic areas onNick’s farm. The council has a permit(PER9076) for the use of Verdict*, and

� Hymenachne flourishes in low-lying areas inthe Cardwell shire

� Nick’s sugarcane was badly contaminated byhymenachne

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reports much better control when using thisherbicide compared to glyphosate. WhileRoundup® Biactive™ (glyphosate) providessome control of hymenachne, the CardwellShire Council reports that its non-selectiverange has resulted in damage to non-targetspecies. Verdict* is a grass-selectiveherbicide and does not damage othervegetation, including native sedges.

From 1999 to 2005, Nick monitored andcontrolled hymenachne on all his propertiesat least four times per year. This cost himabout $8000 per year, in chemicals, manhours and equipment, though costs havereduced each year as less hymenachneneeds to be controlled.

* Trademark of Dow AgroSciences LLC

Local government roleThe Cardwell Shire Council has beenproactive in the control of hymenachne. All landholders whose land borders onareas treated by the council are informed of these activities, and are urged to controlhymenachne on their properties to preventreinfestation. The council sent letters to alllandholders adjacent to Nick’s propertiesrecommending that they address thehymenachne problem. The council’sQuikspray unit is available to alllandholders for use on hymenachne and, with a 150 m extension hose, mostinfestations along banks and drains can be reached.

ConclusionsAfter seven years of hard work andsignificant expenses, Nick feels that he isachieving success against hymenachne. Hehas now controlled hymenachne on all hisproperties, but says he must remain vigilantto prevent reinfestation.

‘I have beaten it and now have a farm withone less weed,’ Nick said.

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� The Cardwell Shire Council has been proactive in controlling hymenachne and has assisted many landholders such as Nick

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Government andLandcare workingtogetherEradicating hymenachne from anannual lagoon in the Northern Territory

BackgroundThe area known as Lambells Lagoon islocated near the Arnhem highway,approximately 50 km south-east of Darwin.Lambells Lagoon, the wetland of EwartRoad, has progressively been invaded byhymenachne. The weed had covered mostof the lagoon by 2004, to the detriment ofmany native water plants and animals.

How did the weed spread?It is not clear how hymenachne came to be in the lagoon, but there are severalmeans by which it could have spread.Hymenachne is grown on a nearby researchfarm where it is utilised as a pondedpasture. The research farm, though situatedon the Adelaide River floodplain, is notlinked to the lagoon system. The presence of a hymenachne source on this farm,however, may have provided material forspread to the lagoon by either buffalo or by magpie geese.

Humans may also have assisted in thespread of hymenachne, as many peoplehunt near the lagoon. Seed or plantmaterial, transported on quad bikes,motorcycles, boats or vehicles, could havecontributed to the spread of hymenachne.Two other lagoons, located within the samedrainage system during the wet season andin close proximity to Lambells Lagoon, arenot visited by humans and are free ofhymenachne.

PlanningThe local Landcare group were the first toreport hymenachne growing in the lagoon.In August 2004, the invasive weed waspositively identified as Hymenachneamplexicaulis by Northern TerritoryGovernment staff. The Landcare group,concerned by the widespread infestation ofhymenachne, wanted to restore the area toits natural state. The group was prepared tomaintain the site if the initial weed densitycould be reduced to a manageable quantity.

The eradication of hymenachne fromLambells Lagoon required careful planning.The planning process involved the localLandcare group, staff from the Departmentof Natural Resources, Environment and theArts (NRETA) and staff from the PastoralManagement Branch of the Department of Primary Industries, Fisheries and Mines(DPIFM).

Extensive research identified suitable controloptions, with stage one of the controlprogram commencing in October 2004. Thecontrol of hymenachne was a collaborativeeffort between government agencies andLandcare.

Controlling hymenachneHymenachne was first sprayed withWeedmaster® Duo (glyphosate 360 g/L at 1 L per 100 L water), which took twooperators three hours to cover the entirearea. Boom sprays and a vehicle-mountedspray tank were used in this operation.

Within three weeks of application, thehymenachne was dying off and much of itsheight had collapsed. The hymenachne wasleft for another month, and was then burntto remove the bulk of dead matter andprovide access for follow-up control.

Burning was followed with anotherchemical application of Roundup® Biactive™

(glyphosate 360 g/L at 1 L per 100 L water)to control emerging seedlings. The follow-up control took much less time andherbicide, with two operators taking onlyone hour to spray the same area.

The lagoon refilled over the wet season withonly a few isolated islands of hymenachnesurviving. Free-floating hymenachne wasremoved by boat, with operators usingscoop nets and weed bags. By April 2005,many of the native aquatic speciespreviously displaced by hymenachne hadrecovered in the lagoon.

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� Hymenachne covered most of Lambells Lagoon in 2004

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Impacts on aquatic ecology Before any control measures were carriedout, government agencies and Landcareconducted a general survey of the lagoon.The group used a macroinvertebratesampling sheet (for more information seethe Waterwatch website at<www.waterwatch.org.au/publications/module3/macroinvertebrates.html>) to determinethe type of macroinvertebrates present,which gave a general idea of the health ofthe lagoon. This activity clearlydemonstrated the adverse effectshymenachne had on aquatic life in thelagoon and highlighted the reason foreradicating hymenachne from this area.

The same study was repeated after all themethods to control hymenachne werecarried out. This time the study found thatthe number of species in and around thelagoon had markedly increased. Thissuggested that the timing and application ofall methods undertaken by the group,including the use of herbicides registeredfor waterway use, had little or no residualeffects on native aquatic species. It alsodemonstrated the impact hymenachne canhave on the ecology of aquatic areas, andhow quickly the affected area recovers oncethis weed is removed.

Successful outcomesIn less than one year, the original weedinfestation was reduced to three containedislands. This left a manageable area to becontrolled during the following dry season.The local Landcare group will continue tomonitor and control the hymenachne atLambells Lagoon.

This case study illustrates how a problemweed can be controlled through thesuccessful collaboration of government andcommunity. It also demonstrates thatintegrated weed control, using herbicides,fire and manual control, can achieve thedesired outcomes.

� Hymenachne was sprayed with Weedmaster® Duo

� Three weeks after herbicide application, much of the grass had died off

� In less than one year hymenachne was drastically reduced to a level that could be managed

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Does chemical controlof hymenachne affectwater quality? Findings from a research project inMackay, Queensland

IntroductionA collaborative research trial in thefreshwater Sandringham Lagoon Wetlandwas conducted over a six-month period in2003–04. The study was designed aroundthe needs of sugarcane growers and landmanagers, and focused on developing bestmanagement practices for the chemicaleradication of hymenachne at farm scale.

Sandringham Lagoon is situatedapproximately 15 km south of the city of Mackay. This small coastal lagoon is longand narrow, and, while it makes up onlyabout 11 hectares, it is approximately 8 kmin length. The lagoon flows directly intoSandringham Bay, which forms part of theSouth Pacific Ocean. Average rainfall in thisregion is approximately 1600 mm per year.

Collaborators in this project included theDepartment of Natural Resources, Minesand Water, CANEGROWERS (QueenslandCane Growers’ Council), the PioneerIntegrated Catchment ManagementAssociation, the Mackay Area ProductivityServices and the Mackay City Council.

Project aimsThis study aimed to determine how muchhymenachne could be successfullycontrolled during a spray event withoutcausing adverse impacts on water quality.

Sites and control methodsLand managers generally controlhymenachne with a ‘blanket’ spray of thewhole infested area. This project, however,was designed to spray only a percentage ofthe weed at the given site instead of aimingfor total coverage. This was achieved asfollows:

• Site 1 was not sprayed and was referred to as the control site.

• At Site 2, 25% of the site was sprayed. For each chemical application, only 25% of the hymenachne covering that site was actually sprayed. Follow-up spraying of regrowth occurred in the same percentage where necessary—the same principle was followed at Sites 3 and 4. Site 2 was sprayed a total of eight times.

• At Site 3, 33% of the weed was sprayed. The chemical was applied a total of six times.

• At Site 4, 50% of the weed was sprayed and the chemical was applied four times.

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The herbicide used was Monsanto’sRoundup® Biactive™ (360g/L glyphosate).Spraying and monitoring occurred in thewet season from October 2003 to March 2004.

Monitoring water qualityWater quality sampling was conducted at all four sites, and measurements ofdissolved oxygen, pH, electricalconductivity and temperature were taken.Apart from the four experimental sites,water quality testing was done at a site thathad 100% hymenachne cover.

Dissolved oxygen is deemed the criticalparameter in aquatic environments and isvital to life in the aquatic ecosystem. Theexpected daily trends for dissolved oxygenwere observed at all sites prior to spraying,but these levels changed after the sites weretreated. Two weeks after spraying, thedissolved oxygen levels at these sites haddecreased markedly. This is becausedecomposition processes consume oxygenand the larger the organic load, the moreoxygen is required to decompose thismatter. Dissolved oxygen levels continuedto decline, and the impact of hymenachnedeath typically took one month to fullyregister.

The greatest impact on dissolved oxygenoccurred at Site 4, where the largestpercentage of hymenachne was controlled.Although a large amount of hymenachnewas killed, the decomposing matterconsumed dissolved oxygen and depletedwater quality.

The smallest impact on dissolved oxygenwas at Site 2, where the least amount ofhymenachne was treated. Because lesshymenachne was treated, the impacts ofdecomposing material on water qualitywere minimised. Controlling largehymenachne infestations with this strategy is not likely to be economical, however, as the remaining hymenachne plants canregrow quickly.

The most effective hymenachne control inSandringham Lagoon occurred at Site 3,where 33% of the hymenachne wassprayed. This maximised the amount ofhymenachne killed, but minimised the lossof dissolved oxygen.

� Location of the four test sites

� Controlling large areas of hymenachne nextto water can have detrimental impacts onwater quality

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It is also interesting to note that the site with100% hymenachne cover had lowerdissolved oxygen readings than the lowestlevels recorded in the treated sites. Thissuggests that the ‘do nothing’ approach isnot effective in managing this weed, andcontributes to further degradation of aquaticecosystems. There was a noticeable loss ofbiodiversity at this site, and the lowdissolved oxygen levels contributed to theloss of fish and native invertebrates. Thephysical clogging of the wetland alsoresulted in the loss of roosting and feedingareas for birds.

Other water quality parameters testedshowed little adverse affect on the aquaticecosystem. Water temperature showed no discernable relationship with the deathof hymenachne. Electrical conductivityresults were broadly similar throughout thetesting and had no impact on aquatic life.Tests proved that pH levels were all withinacceptable limits and correlated to naturalcycles. The death of large areas ofhymenachne caused some shift in pH dueto the release of organic acids, but this shiftwas low and not expected to harm aquaticlife in the lagoon.

Key outcomesThe study of hymenachne eradication withinSandringham Lagoon provided evidenceand conclusions that can be applied toother freshwater bodies in the region. Bestmanagement practices should be guided byfour conclusions:

• The ‘do nothing’ approach is not an effective management system for hymenachne.

• The best practice is to spray hymenachne when there is no water. If there is water present, the death of large quantities of hymenachne will result in a decrease of dissolved oxygen. Where 50% of the site was sprayed (Site 4) dissolved oxygen levels only started to recover after four months. A staggered spraying regime, between three and four months, will limit the drop in dissolved oxygen.

• For small infestations of hymenachne, the most effective spraying regime is to spray one quarter of the weed each month, for four months. This will result in effective weed kill and limit the drop in dissolved oxygen.

• In areas where hymenachne has infested 40–50% of the total area, the best approach is to spray a third of the infestation every month over a three-month period.

This case study is a summary of anunpublished report by Edward Oldmeadowand Cassandra Chopping titled ‘Towards afarm scale best management practice for the eradication of the noxious weedHymenachne amplexicaulis in SandringhamLagoon, Mackay, Queensland’.

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� Levels of dissolved oxygen at each site before and after treatment

The value ofhymenachne to the grazier

BackgroundWambiana, owned and managed by Johnand Ronda Lyons, is a 23 200 hectareproperty near Charters Towers in NorthQueensland. This breeding and fatteningproperty has been owned and operated bythe Lyons family since 1912. The propertyruns 3000 head of cattle in an averageseason. Rainfall in the area averages 625 mm per year, but can vary significantly.

The Lyons family, like many graziers innorthern Australia, have searched for waysof overcoming the effects of the annual dry.Cattle lose weight in the dry season whennative pastures lack quality, even in years of average rainfall. The system of pondedpastures allows the storage of run-off waterto produce fodder in the dry season, which

reduces the annual protein droughtexperienced by graziers between May and December.

Ponded pasturesPonded pastures were established onWambiana in the mid 1980s. The firstsystem of ponds contained para grass, but although this plant was useful, it hadlimitations. Para grass grew well in water upto 30 cm deep, but this only accounted for20% of the ponded area and left the other80% wasted.

John Lyons first saw hymenachne at Granite Vale, the property of Joe Olive, at Marlborough during a field day in May1987. John was impressed by the plant’sability to grow in deeper water andobtained some hymenachne runners for planting on his property.

Planting hymenachneThe first runners of hymenachne wereplanted on Wambiana in a small dam nearthe house. The family also established anursery to produce runners for replanting in the larger ponds.

Initial establishment of hymenachne fromrunners was an outstanding success as aresult of favourable seasonal conditions. The clear pond water also allowed good sunpenetration, which accelerated plantgrowth.

To improve planting efficiency, the Lyonsfamily designed and constructed a plantingmachine pulled by a four-wheel motorbike.This proved very successful, and the plansfor this machine have been distributed as far as Darwin.

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The area under hymenachne on Wambianafluctuates between 38 and 78 hectares,depending on the season. All thehymenachne is grown in a ponded pasturesystem and it grows well year-round,provided there is enough moisture. Othergrasses in the ponded system include nativecouch grass, aleman grass and para grass,with the latter dominating the shallow waterand edges of the pond.

The advantages of hymenachneHymenachne produces twice the bulk ofpara grass or aleman grass on Wambiana.This has resulted in the improved carryingcapacity of one beast per hectare for sixmonths of the year. This is not only fivetimes better than results from native grasses,but hymenachne also provides quality feedto grow cattle in the dry season.

In years with sufficient rainfall to providerun-off into the ponds, the Lyons’ canincrease their stocking rate. John said, ‘I have not found anything to match thecarrying capacity or advantages of theponded system, provided you have thecountry and climate to suit.’ The ponds stillwork in years of low rainfall, but to areduced capacity.

Wambiana’s ponded pastures are designedto overcome weight loss of weaners, andhymenachne is a cheap and highlysuccessful weaner feed. The need topurchase molasses or protein meal, whichcan be a weakness in animal production, is alleviated by the use of ponded pastures.

Managing spread of hymenachneJohn said that there is a possibility thathymenachne could spread along waterways,but he has seen no evidence of it spreadingfrom his property. John is aware that birdsand ducks can spread the seed and he hasseen hymenachne at isolated waterholesand dams. However, he says theseinfestations never survive due to dryweather and heavy grazing by cattle.

Hymenachne is not likely to become aweed because ‘the harsh, dry environmentand its appeal to cattle do the managing for us’, John said.

The futureJohn recognises that hymenachne is aproblem weed on the coast, but, in hisenvironment, it is a valuable grass and an asset to animal production.

If hymenachne was no longer available as a pasture grass, the Lyons family would haveto rely on aleman grass or let native watergrasses take their place in the pondedpasture. Neither are preferred options, norwill they provide the benefits thathymenachne does to cattle production onWambiana.

John believes that the loss of hymenachnewould remove a cheap, natural supplementthat grows automatically in favourableyears. Replacing hymenachne withexpensive supplements would increaserunning costs, and 50% of the capitalinvestment of $50 000 to create the pondsystem would also be lost.

Please Note.This manual does not endorse the use of hymenachne. Hymenachne is a declared weed.Refer to page 3 for your State/Territory legislation

Controllinghymenachne inHorseshoe and Pink Lily lagoons A collaborative project in NorthQueensland

BackgroundHorseshoe Lagoon is an important fish-breeding and fauna conservation site ofaround 102 hectares. Pink Lily Lagoon, also noted as a fish-breeding site, comprises 90 hectares. Both wetlands provide ahabitat for native and migratory birds aswell as many ground-dwelling frogs andreptiles. The wetlands are fringed by canefarms and grazing lands, and are situated in close proximity to the small sugar townof Giru in the Burdekin Shire.

Hymenachne is still utilised as cattle feedby graziers in the Burdekin region. It isbelieved that its spread to the wetlands wasaided by waterfowl and other native birds.Three years of above average wet seasons in the late 1990s caused an alarmingexpansion of hymenachne within theselagoons.

Collaboration and planningFollowing a successful bid by the BurdekinShire Council for Australian Governmentfunding in September 2001, a managementcommittee was formed to coordinatehymenachne control for the lagoons. This committee comprised landholders,representatives of government agencies,local sugar mills, SunWater, irrigators and fish restockers.

The management committee providedinformation about the sites beforehymenachne had invaded the wetlands,including survey maps showing theestimated boundaries of the lagoons. Largeareas of open water had existed in 1995.The committee used this information todetermine how much weed control wouldbe necessary to return the lagoons to theiroriginal conditions.

Before treatment occurred, the extent of the weed infestation was determined and photographed, and three permanentphotograph points were established. Aerialphotographs and Geographical InformationSystem (GIS) mapping of the sites providedbenchmarks for future monitoring andevaluation.

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The committee liaised with landholders,including traditional owners, in thedevelopment of plans to controlhymenachne in the lagoons. All landholdersstrongly supported the control ofhymenachne in these wetlands.

ControlIn April 2002, work commenced with on-ground and aerial spraying of lagoons andadjoining areas. An aerial spray permit forthe use of Roundup® Biactive™ was obtainedfrom the APVMA. Aerial application, whichwas expensive, was only used in areasimpossible to reach by conventionalvehicles or watercraft.

An excavator was used initially to provideaccess to the lagoons for the sprayequipment. Infestations along the bankswere removed and channel banks wereformed to allow access for on-groundoperators and monitoring personnel. Land-based treatment of hymenachne waslimited and dangerous, as it was oftendifficult to see where the land ended

and the water began.

The herbicide used for all chemical controloperations was Roundup Biactive(glyphosate 360 g/L) at a maximum rate of 14 L/ha, which provided consistentresults in the order of 90% control ofhymenachne eradication.

Manual removal of hymenachne made up a significant part of the control program.Weed harvesters and weed rakes were ableto remove large sections of hymenachneand create areas of open water in thelagoons. More isolated areas ofhymenachne that surrounded the openwater were then treated with herbicideapplications from a boat.

Hymenachne was found growing onfloating mats of water hyacinth. These matsvaried in size from several plants to about800 m2, and would move from one end ofthe lagoon to the other with the prevailingwinds. The Burdekin Shire Council usedtheir weed harvester to push large rafts ofhymenachne and water hyacinth to theedges of the lagoon. An excavator, mountedwith a weed rake, moved these weeds fromthe water onto the banks.

Rather than burning or disposing of theweed matter, a landholder incorporated this green waste into his cane paddocksprior to planting. By the time he planted hissugarcane, much of the material haddecomposed. The addition of this greenmanure greatly improved soil fertility andresulted in the grower obtaining double hisaverage yields for sugarcane the followingyear.

� The lagoons were infested by hymenachne and other aquatic weeds

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Follow-up and monitoringAll infestations required regular follow-upcontrol and monitoring. The permanentphotograph points showed the progressmade by the control operation. Monitoringconsisted of visiting sites, where infestedand successfully controlled areas wererecorded. Quarterly boat surveys and half-yearly aerial photographs also assisted withthis process.

Monitoring has helped identify new threats.Reinfestation of hymenachne fromsurrounding waterways by wildlife andfloods was identified as an ongoing threat in this area. Evidence of the cabomba weed(Cabomba caroliniana) in the lagoons wasalso a potential problem due to an increasein open water.

The monitoring process of the lagoons andsurrounding areas has continued since thisproject was completed.

Promoting the benefitsThe benefits of control were promoted to

local land managers to encourage follow-upcontrol of hymenachne. Regular meetingswith landholders kept them informed ofchemical use, control costs, recordingrequirements, and results from site visitsand monitoring. Management committeeminutes, Waterwatch information and fishsurveys were also discussed duringmeetings with landholders.

The Burdekin Shire Council providedherbicide subsidies to landholders whodemonstrated an ongoing commitment to the eradication of hymenachne in the lagoons. Close collaboration withlandholders has raised the awareness of theenvironmental impacts of hymenachne andhas underlined the need for control.

The region-wide value of the control projectwas presented to the community at local

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� The Burdekin Shire weed harvester removeshymenachne and water hyacinth

� Large areas of hymenachne were removed by excavator and weed harvester

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shows, agricultural field days, and throughlocal media and signage. The BurdekinShire Council also obtained an interactivetouch-screen computer that informs thepublic of the threat of hymenachne and thecontrol measures undertaken in the shire.

Benefits and future workThe removal of large areas of hymenachnefrom the lagoon had broad biodiversitybenefits in the region, such as:

• improved water quality• an increase in fish populations• recolonisation of native plants

and wildlife• reinstatement of the native food chain.

This two-year project promoted theenvironmental benefits of hymenachnecontrol to the broader community, and alsoprovided an excellent example for otherareas with similar problems. Landholderswere actively involved in controllinghymenachne, and many will continue to do so as participants of the lagoons’maintenance group.

Although large areas of hymenachne havebeen removed from these lagoons, theeradication of aquatic weeds remains anongoing task. Other land managementstrategies, such as fencing, grazing andreplanting of riparian vegetation, have nowbeen included in ongoing plans to eradicate

� Control of hymenachne created large areas of open water which led to improved water quality and an increase in fish populations

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� Hymenachne (dark green) invading a water storage area

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� Hymenachne reduces aesthetic values and recreational opportunities

Enquiries about declared weeds should firstbe referred to your relevant localgovernment, shire council or stategovernment department.

Hymenachne information sheets can beobtained from the following agencies.

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Further informationS e c t i o n 5

Table 2: General contact details

Organisation/department Contact details

Department of Natural Resources, Mines and Water (Queensland)

Weeds Australia

Cooperative Research Centre for AustralianWeed Management

Phone: 1800 803 788Website: www.nrm.qld.gov.au

Website: www.weeds.org.au

Phone: 08 8303 6590Email: crcweeds@adelaide.edu.auWebsite: www.weeds.crc.org.au

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Table 4: State and territory contact details

Organisation/department Contact details

New South WalesDepartment of Agriculture

Department of Infrastructure, Planning andNatural Resources

Northern TerritoryDepartment of Natural Resources, Environment and the Arts

Parks and Wildlife (for information onprohibited entrants)

QueenslandDepartment of Natural Resources, Mines and Water

South AustraliaDepartment of Primary Industries and Resources

TasmaniaDepartment of Primary Industries, Water andEnvironment

VictoriaDepartment of Primary Industries

Western AustraliaDepartment of Agriculture

Phone: 02 6391 3100Email: dpi.nsw@dpi.nsw.gov.auWebsite: www.dpi.nsw.gov.au

Phone: 02 9762 8044Email: information@dipnr.nsw.gov.auWebsite: www.dipnr.nsw.gov.au

Phone: 08 8999 2020Email: weedinfo.nreta@nt.gov.auWebsite: www.nt.gov.au/nreta

Phone: 08 8999 5511Website: www.nt.gov.au/ipe/pwcnt

Phone: 1800 803 788Website: www.nrm.qld.gov.au

Phone: 08 8226 0222Website: www.pir.sa.gov.au

Phone: 1300 368 550Website: www.tas.gov.au

Phone: 136 186Email: customer.service@dpi.vic.gov.auWebsite: www.dpi.vic.gov.au

Phone: 08 9368 3333Email: enquiries@agric.wa.gov.auWebsite: www.agric.wa.gov.au

Reference listAgriculture and Resource ManagementCouncil of Australia and New Zealand,Australian and New Zealand Environmentand Conservation Council & ForestryMinisters 2000, Weeds of NationalSignificance: hymenachne (Hymenachneamplexicaulis) strategic plan, NationalWeeds Strategy Executive Committee,Launceston.

Ainsworth, N & Bowcher, A 2005,Guidelines, herbicides: guidelines for use inand around water, CRC for Australian WeedManagement, Glen Osmond, SouthAustralia.

Akacich, B, Sibley, N, Graham, M &McLachlan, K 2005, ‘The effectiveness ofcattle grazing as an exotic pasturemanagement tool in the TownsvilleCommon Environmental Park’, 8thQueensland Weed Symposium proceedings,Weed Society of Queensland Inc.,Townsville, p. 99.

Anning, P & Kernot, J (comps) 1989,Ponded pastures, North Queensland beefproduction, Queensland Department ofPrimary Industries & Dalrymple Land CareCommittee, Charters Towers.

Brambila, J & Santana, FJ 2004, ‘Firstrecords for Ischnodemus variegatus(Hemiptera: Blissidae) in North America’,Florida Entomologist, vol. 87, no. 4, pp.585–586.

Bunn, SE, Davies, PM, Kellaway, DM &Prosser, IP 1998, ‘Influence of invasivemacrophytes on channel morphology andhydrology in an open tropical lowlandstream, and potential control by riparianshading’, Freshwater Biology, vol. 39, no. 1,pp. 171–178.

Cameron, AG 2003 ‘Hymenachne’, Agnote,no. 549, E33, Agdex, no. 131/32, NorthernTerritory Government, Darwin.

Cooperative Research Centre for AustralianWeed Management & CommonwealthDepartment of Environment and Heritage2003, Weeds of National Significance weedmanagement guide: hymenachne or OliveHymenachne (Hymenachne amplexicaulis),Cooperative Research Centre for AustralianWeed Management, Glen Osmond, SouthAustralia.

Csurhes, SM, Mackey, AP & Fitzsimmons, L 1999, Hymenachne (Hymenachneamplexicaulis) in Queensland, LandProtection pest status review series,Department of Natural Resources, Brisbane.

Department of Natural Resources andMines 2003, Policy for development anduse of ponded pastures, QueenslandGovernment, Brisbane, viewed 15December 2005,<http://www.nrm.qld.gov.au/about/policy/documents/1291/lmu_2003_1291.pdf>.

Department of Primary Production, Divisionof Agriculture and Stock 1981,‘Hymenachne acutigluma in the NorthernTerritory’, Technical Bulletin, no. 46,Northern Territory Government, Darwin.

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Douglas, MM & O’Connor, RA 1999,‘Effects of para grass (Urochloa mutica(Forssk.) TQ Nguyen) invasion on terrestrialinvertebrates of a tropical floodplain’,Proceedings of the 14th Australian WeedsConference, Weed Society of New SouthWales, Sydney, pp. 153–156.

——2004, ‘Weed invasion changes fuelcharacteristics: para grass (Urochloa mutica(Forssk.) TQ Nguyen) on a tropicalfloodplain’, Ecological Management andRestoration, vol. 5, pp. 143–145.

Grace, BS, Gardener, MR & Cameron, AG2004, ‘Pest or pasture? Introduced pasturegrasses in the Northern Territory’,Proceedings of the 14th Australian WeedsConference, Weed Society of New SouthWales, pp. 157–160.

Helfich, LA, Neves, RL, Libey, G &Newcomb, T 2000, Control methods foraquatic plants in ponds and lakes, VirginiaCooperative Extension, Virginia StateUniversity, Petersburg, Virginia.

Kibbler, H 1997, Physiological adaptationsof Hymenachne amplexicaulis andHymenachne acutigluma to flooding, The University of Queensland, St Lucia,Queensland.

Land Protection 2006, ‘Hymenachne(Hymenachne amplexicaulis)’, Fact sheetPP54, Department of Natural Resources,Mines and Water, Brisbane, viewed 2February 2006,<http://www.nrm.qld.gov.au/factsheets/pdf/pest/pp54.pdf>.

Lemcke, B 1995, ‘Aleman grass: a grass forflooded or ponded pastures’, Agnote, no.642, E53, Agdex, no.131/32, NorthernTerritory Government, Darwin.

O’Donnell, K 2004, Cattle and fire to limitwetland invader, Tropical Savannas CRC,Darwin, viewed 2 February 2006,<http://savanna.ntu.edu.au/publications/savanna_links30/para_grass.html>.

Oldmeadow, E & Chopping, C 2005,‘Towards a farm scale best managementpractice for the eradication of the noxiousweed Hymenachne amplexicaulis inSandringham Lagoon, Mackay,Queensland’, unpublished report,Department of Natural Resources, Minesand Water, Mackay–Whitsunday Region.

Overholt, WA, Ewe, SML, Diaz, R, Morgan,EC & Moeri, OE 2004, ‘Feeding effects ofIschnodemus variegatus (Hemiptera:Blissidae) on photosynthesis and growth ofHymenachne amplexicaulis (Poaceae),Florida Entomologist, vol. 87, no. 3, pp. 312–316.

Petroeschevsky, A 2005, ‘Managementpriorities for reducing the threat of theaquatic Weeds of National Significance’,8th Queensland Weed Symposiumproceedings, Weed Society of QueenslandInc., Townsville, pp. 110–113.

Tropical Weeds Research Centre 2004,Hymenachne (Hymenachne amplexicaulis)control and management in Queensland,Department of Natural Resources andMines, Brisbane, viewed 2 February 2006,<http://www.nrm.qld.gov.au/tropical_weeds/projects/hymenachnecontrol.html>.

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Russell-Smith, J n.d., Indigenous firepractice in western Arnhem Land: Lessonsfor today, Tropical Savannas CooperativeResearch Centre, Darwin, viewed 14 February 2006,<http://www.savanna.ntu.edu.au/downloads/indfire.pdf>.

Searle, T & Fell, R n.d., Native grass speciesfor revegetation, Tropical SavannasCooperative Research Centre, Darwin,viewed 10 February 2006,<www.savanna.ntu.edu.au/downloads/melnat.pdf>.

Van Klinken, R, Panetta, FD, Ross, B, &Wilson, C 2004, ‘A pain in the grass: what’sthe diagnosis?’ Proceedings of the 14thAustralian Weeds Conference, WeedSociety of New South Wales, Sydney, pp. 480–483.

Vitelli, J Madigan, B & Ruddle, L 2005,‘Chemical breakdown of a herbicide in acontrolled aquatic environment’, 8thQueensland Weed Symposium proceedings,Weed Society of Queensland Inc.,Townsville, pp. 63-68.>.

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Appendix 1

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