What’s New In Biological Control of Weeds? Issue 13, Nov 1999 · Canadian colleagues tell us that they too are disappointed with the performance of the Californian thistle leaf

What’s Inside?

International Hot Gossip 1

Local Hot Gossip 4

The Four CountryComparison from Hell 5

More Millennium Bugs 6

Tell Me More... 9

Summer Activities 10

As this is the lastnewsletter for 1999 theteam at Landcare Researchwould like to take thisopportunity to wisheveryone a very happyChristmas and amemorable New Year.See you in the newmillennium!

Chelsea Helps to Purge

Spurge

After a week of non-stoptalking about biologicalcontrol projects, at theMontana State University inBozeman, it was great to getout in the field and see someof these projects in the flesh.The post-symposium field tripwas also a wonderfulopportunity to experience thebreathtaking scenery andwildlife of the RockyMountains and a bit of WildWest culture. In our travels we

Manaaki WhenuaLandcare Research

Number 13 November 1999

What’s New In Biological Control of Weeds?

visited a 45,000 acre AberdeenAngus cattle ranch where amajor pest, leafy spurge

(Euphorbia esula), is beingsuccessfully controlled using acombination of beetles(Apthona spp.) and a smallflock of sheep. The sheep haveto be guarded 24 hours a dayby a shepherd and three dogsto keep them safe from bears,cougars and coyotes! Much toour surprise we ran intoChelsea Clinton doing workexperience on the ranch. Shehad spent the day mendingfences and doing her bit to

A rancher shows biological control expertsfrom around the world the agents that aresuccessfully reducing his leafy spurge problem

International Hot Gossip

In July a New Zealandcontingent travelled to theWild West American State ofMontana (known affectionatelyas “the last best place”) to takethe opportunity to live, breathe,and sleep biological control ofweeds with researchers fromall over the world. Thisinternational symposium isheld every 3–4 years and is anextremely important way ofmaintaining the excellentinternational collaboration thatbiological control of weeds isrenowned for. Below, we havelisted some of the pearls ofwisdom gleaned from thismeeting that are of particularinterest to New Zealand.

What's New in Biological Control of Weeds? Number 13 November 1999

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believe they are sitting on atime bomb. It can only be amatter of time before newinfestations appear in newareas, and when it comes tothe crunch we are going toneed better tools to be able todeal with them.

A discussion group was heldone evening to discuss waterweeds and the ongoing problemof alligator weed came up.Apparently surveys in SouthAmerica in the 1960s revealedat least 60 insect speciesassociated with alligatorweed, but little, if anything, isknown about most of thesespecies. There is a goodchance that further surveyswould turn up many potentialbiological control agents.Other potential agents alreadyexist. For example, Americancolleagues told us that a thrips(Amynothrips andersoni) thatdamages terrestrialinfestations is showing somepromise. Also the terrestrially

orientated flea beetle(Disonycha argentinensis) mightbe worth giving another try.The beetle previously failed toestablish down under, but itcan often take severalattempts to establish a controlagent. There is also thepossibility of finding suitablepathogens to attack alligatorweed, and a damaging fungus(Nipia alternaria) has alreadybeen identified in Florida.A lot more could be done toadd teeth to the alligatorweed programme.

Alligator weed moth larva

purge spurge by collectingbeetles for redistribution. OurAmerican colleagues hoped thatshe would go home and put ina good word about biologicalcontrol with father Bill.

Alligator Weed — The

Crunch is Yet to Come!

Partial control of alligator

weed (Alternanthera

philoxeroides) has been achieveddown under with a beetle(Agasicles hygrophila) and amoth (Arcola malloi), but theyare not effective in all situations,and in particular terrestrialinfestations continue to beproblematic. It has recentlycome to light that people onboth sides of the Tasman havemistaken alligator weed for A.

sessalis, a popular leafy herb inSri Lanka, and they have beencultivating and spreading itaround. Australian researcherstell us that since they discoveredalligator weed being sold atvegetable markets and evenavailable by mail order they

Gorse Spider Mites

Take A Nose Dive

In issue number 9 of thisnewsletter we showed yousome spectacular photos ofgorse spider mites

(Tetranychus lintearius) inOregon, USA. We were greenwith envy that the mites,which we had supplied themwith, were so much morespectacular than their relativesback here in New Zealand. Atthe time the photos weretaken the colonies were freefrom predators, but this is nolonger the case. History hasrepeated itself and the samepredatory mite (Phytoseiulus

persimilis) and little blackladybird (Stethorus sp.) thatattack gorse spider mites inNew Zealand are nowchomping into the Americanones and unfortunatelylimiting their effectiveness too.


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Privet Gets Up People’s

Noses

Every year regional councils’phones ring red hot withpeople complaining that tree

privet (Ligustrum lucidum) andChinese privet (Ligustrum

sinense) are giving them hayfever and asthma. While it hasbeen easy to point the fingerat privet, it has been moredifficult to prove that theseplants are indeed the culprits,since both are insect-pollinated and do not producethe sorts of wind-blownpollen commonly associatedwith these conditions.However, our UK colleaguestold us that other members ofthe Oleaceae family have beenshown to produce pollen thatis harmful to humans. Forexample, the European olive(Olea europaea) is an importantcause of snuffles and wheezes

in the Mediterranean area.Its pollen has been foundto contain an allergenknown as Ole e-I, and

similar substances areknown to exist in other

members of the Oleaceaefamily that could wellbe allergenic too.

Around the globemore and more people arebecoming concerned about theimpacts of various privetspecies, and the plant now haspest status in Argentina,Australia, Brazil, southernUSA, and on the islands ofMauritius and La Réunion.Ligustrum robustum ssp.walkeri is so invasive on LaRéunion that a biologicalcontrol programme has beeninitiated to try to save theisland’s forest ecosystems. Adiscussion group was heldduring the symposium whereseveral countries talked aboutthe possibility of collaboratingto expand this privet work. Asa first step towards thispotential collaboration we willproduce a report this year onthe feasibility of implementinga biological controlprogramme in New Zealand.

Chinese tree privet

A Thorny Issue

Canadian colleagues tell usthat they too are disappointedwith the performance of theCalifornian thistle leaf beetle Californian thistle leaf beetle

(Lema cyanella). Because thisfoliage-feeding beetle mightalso attack some of their nativethistles, they are going to cuttheir losses and try to eradicateit! There was a lot of talk atthe symposium about theimpact of the nodding thistlereceptacle weevil (Rhinocyllus

conicus) on native thistles inNorth America, and we sawthe evidence ourselves whileexploring YellowstoneNational Park. Even thoughsafety testing showed that thenative thistles were at risk, adecision was made in the1960s to release the weevilsanyway. It wasn’t until nearly30 years later that the riskbecame a reality. Thankgoodness we don’t have anynative thistles in New Zealandto complicate matters!


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Wilding Pines

In issue number 11 of thisnewsletter we told you aboutthe South African project tocontrol wattles which are,amongst other things, suckingtheir rivers dry of water.Wattles aren’t the onlyculprits and other trees mustbe controlled too. SouthAfrican researchers told us

There have been big smiles allround as the mist flower

fungus (Entyloma ageratinae)exceeds expectations. Thewhite smut was released forthe first time last summer andthere were promising resultsby autumn when it looked asthough it was successfullyestablishing at all nine releasesites. Knowing that the fungus

Local Hot Gossip

that they are exploring thepossibility of developingbiological control for wilding

pines. They intend to focus onfinding seed-feeding agents toprevent both the spread ofinvasive pines into new areasand to prevent areas, whichhave been cleared at greatexpense, from becomingreinfested. A number of

issues are being workedthrough with the forestindustry, such as theprotection of seed orchardsand the possibility thatbiological control agents mightspread tree diseases. Since NewZealand also has a significantproblem with wilding pines,we will be following theirprogress closely.

is most active in warmertemperatures, we expected itto be dormant over the coolerwinter months and did notexpect to see any spectaculardamage until the followingspring. However, this has notproved to be the case! Thewhite smut has been busyduring the winter and largepatches of mist flower are

already severely defoliated atsome sites. Damaged mistflower plants are attemptingto regrow, but new growth,and seedlings, are quicklybecoming infected too. Evenmore pleasing is the sight ofyoung native plants comingaway where once there wasonly mist flower!

Simon Fowler surrounded by diseased mist flower in the Waitakeres


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If you cast your memory backseveral years you mayremember that we askedpeople to send in weed seedsfor an internationalexperiment affectionatelyreferred to as “The fourcountry comparison fromhell”. For years people havespeculated about whetherplants become more invasivewhen grown outside theirnative range because theyevolve into more aggressivestrains, or whether they aresimply responding to morebenign environmentalconditions and, in particular,freedom from their naturalenemies. Dr Tony Willis ofCSIRO, Australia, and Dr Jane

Memmott of BristolUniversity, UK, designedsome experiments to come upwith some answers to thisage-old question.

Tony and Jane decided to testfour plant species — foxglove(Digitalis purpurea), viper’sbugloss (Echium vulgare),

nodding thistle (Carduus

nutans), and ragwort (Senecio

jacobaea) — that are native tothe UK and continentalEurope and introduced weedsin New Zealand andAustralia. Some of the seedssourced from each part of theworld were planted out sideby side in a special plot at theCABI Biosciences

headquarters at Silwood Park,UK. The resulting plants weretended lovingly until maturityso a series of comparativemeasurements could be made.“As a general rule, when keptunder identical conditions theplants all grew pretty muchthe same,” said Jane. “It didn’tseem to matter where theseeds came from.”

The balance of the seedswere used in a tandem

study in which one ofJane’s students, AdamBirchall, compared

their relative sizes. Largeseeds can give plants a headstart in life by providing extraresources for germination andearly growth of seedlings. Ifthe seeds collected from downunder could be shown to belarger than equivalent seedsfrom the UK and Europe, thenthis could explain differencesin behaviour. However, nosignificant difference in thesize of the seeds was detected.

These findings lend supportto the hypothesis that plantsbecome weeds in somecountries because they aresimply responding to morebenign environments andsupport the basic premisebehind biological control thatwe can tame weeds bymaking their lives a little lesscomfortable.

The Four Country Comparison from Hell


6

Banana Passionfruit

Two similar species of banana

passionfruit (Passiflora mixta,

P. mollissima), which originatein the high Andes of SouthAmerica, are becoming seriousinvasive weeds in NewZealand. These should not beconfused with the blackpassionfruit (P. edulis) that isgrown commercially for itsfruit. The weedy ones can becontrolled by cutting andherbicide treatment, but this isnot the total answer becauseof damage to non-targetplants and regrowth fromroots and shoot fragments.Banana passionfruit is also aserious weed in Hawai’i, where

it is known as banana poka. Abiological control programmehas been underway there for anumber of years and two mothspecies and a fungus havebeen released so far. One ofthe moths (Pyrausta perelegans),which attacks the buds,leaves, shoot tips, and youngfruit, has established but notyet had a significant impacton the plant. “The fungus[Septoria passiflorae] was onlyreleased in 1996, but hasalready substantiallydefoliated banana poka atsome sites and lookspromising,” reports SimonFowler, who has beeninvestigating this project.

Other agents in the pipelineinclude a fly that feeds on theflower buds (Zapriotheca nr.nudiseta) and two mothspecies (Josia fluonia, J. ligata)that defoliate the plant.

Information about naturalenemies attacking bananapassionfruit in New Zealandis scarce. This year regional

councils are funding asurvey to find outwhether any potentiallyuseful agents are alreadyhere. For example, a

fungus known as septoriablotch (also called Septoria

passiflorae) has been reportedas causing losses to the P.

edulis industry in NewZealand. “However, wesuspect that, although it hasbeen given the same name, itis not the same species as theone being used as a biologicalcontrol agent in Hawai’i, andit is important to clear up thisconfusion as soon aspossible,” said Simon.

“We only have one nativemember of the Passifloraceaefamily in New Zealand, ko-hia[P. tetandra], and since neitherthis plant nor commerciallygrown passionfruit belong tothe same sub genus as theweedy passionfruits, thenthere is a good chance that wecan find biological controlagents that won’t attack them.”

Hopefully you will all haveread the “Millennium Bugs”story in the last issue of“Weed Clippings” where wesummarised the prospects forbiological control of bone-seed (Chrysanthemoides

monilifera spp. monilifera),climbing asparagus (Asparagus

scandens), and nassellatussock (Nassella trichotoma).In this item we are going tocontinue along this theme andtake a look at the feasibility ofbiological control for anotherthree plants: bananapassionfruit (Passiflora spp.),wild ginger (Hedychium spp.),and woolly nightshade(Solanum mauritianum).

More Millennium Bugs

Banana passionfruit


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Wild Ginger

Kahili ginger (Hedychium

gardnerianum) and yellowginger (Hedychium flavescens)originate from the Himalayas.These fragrant, showy gardenescapees have becomeparticularly invasive in thewarmer parts of NewZealand. Wild ginger speciescan be controlled withherbicide, but this is only cost-effective and environmentallysafe for controlling smallinfestations. Biological controloptions have beeninvestigated in Hawai’ibecause this is nowconsidered the only practicalapproach for the long-termmanagement of kahili gingerin native forests. “A wilt-causing bacterium, Ralstonia

(=Pseudomonas ) solanacearum,that occurs on wild andcultivated ginger (Zingiber

officinale) in Hawai’i, isshowing some potential as acontrol agent there,” reportsHugh Gourlay, after a recentvisit. This soil-borne pathogengets into the plant throughwounds where it causessevere wilting after about 3–4weeks and death and decay ofthe rhizomes after about 4–5months. Recent research hasshown that it is effective at arange of temperatures andmight therefore be of use inNew Zealand.

Not much is known about

other insects and pathogensthat attack wild ginger.Because of its economicimportance, a lot more isknown about the wide rangeof natural enemies ofcultivated ginger. Some ofthese pests and diseases willalso attack wild ginger, forexample, a shoot borer(Conogethes puctiferalis) and aleaf roller (Udaspes folus) havebeen found on Hedychium sp.in India. Several potentiallyuseful fungi have been recordedon species of wild ginger, androt-causing fungi have beenfound attacking gingerrhizomes in New Zealand.

Both wild ginger speciesbelong to the plant familyZingiberaceae. We have nonative plants in NewZealand that belong to thisfamily. The mostimportant members of thisfamily overseas are thecultivated spices (such asginger, cardamom, andturmeric) and, with thepossible exception ofmyoga ginger (a Japaneseculinary delicacy),cultivation of these is notcommercially viable inNew Zealand at present.This is good news as theprocess of developingbiological control agents forginger would be much trickierif it had close relatives ofimportance to New Zealanders.

Overall the prospects forfinding suitable biologicalcontrol agents for wild gingerlook promising. The next stepwould be to survey wild gingerthroughout New Zealand forinsects and diseases, and atthe same time study wildginger in its native India.The pathogens already foundon ginger in New Zealandcould be assessed for theirpotential as mycoherbicides,and the Hawai’ian bacteriacould be tested to see if itwould be suitable to bringinto New Zealand.

Hawai’ian researcher, Rob Anderson,examines a transect where heinfected wild ginger with awilt-causing bacterium. Note in thecentre of the picture the ginger hasbeen killed and regrowth is stuntedcompared to healthy plants inthe background


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Woolly Nightshade

Woolly nightshade has spreadbeyond its native range inSouth America to becomenaturalised in Africa,Australasia, India, and onnumerous small islands. Thissmall poisonous tree (up to 10m tall) is particularly commonin the north of New Zealand.It fruits prolifically throughoutthe year, and birds feeding onthese berries continuallyspread viable seeds. The plantgrows quickly and can fruitand flower within a year ofgermination, forming densethickets that crowd out otherbeneficial plants. Areas clearedof the weed quickly becomereinfested, making long-termcontrol a real headache.

A biological control programmefor woolly nightshade has beenunderway for several years in

South Africa, where it is knownas ‘bug weed’. “Theprogramme has been doggedby complex host-specificityissues,” reports PeterMcGregor, who has been intouch with South Africanresearchers. “There has been afrustrating tendency for manyof the potential control agentsstudied to damage otherSolanum species (particularlyeggplant) in laboratory testseven though they have neverever been known to attackthose plants in field situationsin their native countries.”Laboratory tests in small cagessubject the agents to extremeand unnatural conditions andmay give misleading results.For example, when hosts andnon-hosts are placed closetogether in a small confinedspace, odours from the hostplant may confuse insects intoattacking the non-hosts too. InSouth Africa eggplant cropsare not usually grown close towoolly nightshade, and theyare also heavily sprayed withpesticides and grown inrotation with other crops. Forthese reasons the risk of

damage from woolly nightshadeagents is consideredinsignificant and permissionwas granted recently to allowthe first agent, a sap-suckinglace bug (Gargarphia decoris), tobe released there.

Although woolly nightshadebelongs to the genus Solanum,it is not closely related to other,desirable species of that genusin New Zealand (see tablebelow). It should therefore bepossible to find suitable agentsto introduce here, providedthe host ranges issues can beresolved to everyone’ssatisfaction. We will be keepinga close eye on the lace bugs’every move in South Africa!

Subgenus Members

Brevantherum Woolly nightshade + three other weedy species

e.g., Jerusalem cherry

Archaepsolanum Three native, but not endemic (do not occur

naturally anywhere else), species (e.g., poroporo)

Potatoe Potato, pepino

Lycianthes Eggplant

The fourth set of pagesfor the “BiologicalControl of Weeds Book”was distributed inAugust 1999, covering thetopics of safety andsuccess plus a newmiscellaneous section. Iffor some reason you didnot receive these pages,then please contactLynley Hayes (details onback page). Also,additional copies of theragwort pages have beenprinted and are nowavailable if anyone’sstocks are running low.

Biological Controlof Weeds Book


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Question: Has the old man’s

beard leaf miner taken to

feeding on brassicas?

No! Reports of leaf minersdamaging brassica crops firstappeared in the 1960s, and theculprit is a European fly(Scaptomyza flava). This fly isonly a minor pest in Europe,but it can be a major pest ofbrassicas and peas here.

The old man’s beard leafminer (Phytomyza vitalbae) willonly attack old man’s beard(Clematis vitalba) and possiblycause some slight damage toornamental Clematis species

Tell Me More...

that are closely related to oldmans’ beard. Native Clematis

are not believed to be at risk— they are occasionallymined by a native leaf miner(Phytomyza clematadi).

There are many kinds of leaf-mining insects in NewZealand including flies,moths, beetles, and wasps. Tohelp protect the old man’sbeard leaf miner’s goodreputation we have included atable of some of other leafminer species that you maycommonly see in NewZealand. Note that as ageneral rule introduced leaf

miners tend to only attackintroduced plants and nativeleaf miners tend to only attacknative plants.

Common Name Latin Name Insect Hosts Include

Type

Azalea leaf miner Caloptilia azaleella moth azalea

Beet leaf miner Liriomyza chenopodii fly silver beet, spinach,

chickweed, fathen

Convolvulus leaf miner Bedellia spp. moth convolvulus

Griselinea leaf miner Peristoreus discoideus beetle puka, broadleaf

Eucalyptus leaf miner Phylacteophaga froggatti wasp eucalyptus

Hebe leaf miner Liriomyza spp. fly hebe

Ka-ka- beak leaf miner Liriomyza clianthi fly ka-ka- beak

Karamu- leaf miner Acrocercops zorionella moth coprosma

Kauri leaf miner Acrocercops leucocyma moth kauri

Lancewood leaf miner Acrocercops panacivagans moth lancewood

Oak leaf miner Phyllonorycter messaniella moth oak, beech, birch

Ragwort leaf miner Chromatomyia syngenesiae fly cineraria, sow thistle, senecio,

chrysanthemum

Wattle miner Acrocercops alysidota moth wattle

Ragwort leaf miner


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This newsletter is produced three times a year by:Manaaki Whenua - Landcare Research NZ LtdPO Box 69LincolnNew ZealandPh +64 3 3256 700Fax +643 3252 418

This information may be copied and distributed to others without limitations, provided LandcareResearch and the source of the information in acknowledged. Under no circumstances may achange be made for this information without the expressed permission of Landcare Research

Editor: Lynley HayesLayout: Stacey MitchellCartoons: Anne Rose

ISSN 1173-762X

Manaaki Whenua. Manaaki TangataCare for the land. Care for the people.

Summer Activities

Summer is a good time forharvesting gorse thrips(Sericothrips staphylinus),cinnabar moth caterpillars

(Tyria jacobaeae), and broomseed beetles (Bruchidius

villosus). Refer to the relevantpages in “The Biological

Control of Weeds Book” ifyou are unsure about what

to do. Be careful not tocook your insects by

leaving them out inthe sun in plasticcontainers or in ahot car. Keep the

insects as cool aspossible using chillybins andfreezer pads, and get them totheir new homes as soon asyou can. Avoid havinginsects drown in excessmoisture during transit byusing paper bags orwell-ventilated plasticcontainers filled with tissuepaper. If you areredistributing broom seed

beetles while they arestill inside the pods,you will need to keep a

close eye on poddevelopment. Do notharvest the pods until theyare brown and mature, butbe aware that a spell of hotweather can cause the podsto ripen rapidly andburst open.


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Documents

What’s New In Biological Control of Weeds? Issue 13, Nov 1999 · Canadian colleagues tell us that they too are disappointed with the performance of the Californian thistle leaf