Solanaceous crops, Psyllids \u0026 Liberibacter

$Page 1: Solanaceous crops, Psyllids \u0026 Liberibacter$
Solanaceous Crops

Psyllids & Liberibacter

Proceedings of the Workshop held 26 March 2009Christchurch, New Zealand

“Issues and Opportunities for Collaboration”

Solanaceous Crops – Psyllids & LiberibacterProceedings of the workshop held 16 March 2009, Christchurch, New Zealand7th World Potato Congress

Editor: Warrick NelsonPublisher: The New Zealand Institute for Plant & Food Research Ltd www.plantandfood.co.nz

© 2009 is retained by the respective authors or their employers, otherwise Plant & Food Research.

National Library of New Zealand Cataloguing-in-Publication Data

World Potato Congress (7th : 2009 : Christchurch, N.Z.)

Solanaceous crops, Psyllids & Liberibacter : proceedings of the workshop

held 26 March 2009, Christchurch, New Zealand / [editor, Warrick Nelson].

ISBN 978-0-9864540-0-4

1. Solanaceae—Diseases and pests—Congresses. 2. Jumping plant-lice—

Congresses. I. Nelson, Warrick, 1959- II. Title.

583.952—dc 22

Programme

Welcome Warrick Nelson 1ZC – North American context Gary Secor 4Psyllids – North American context Joe Munyaneza 11Liberibacter and Phytoplasma – New Zealand context Lia Liefting 26Economic impacts, market access and preliminary observations of potato survey

Stephen Ogden and John Fletcher

32

Phytoplasma – Columbia Basin Potato Purple Top Joe Munyaneza 39Industry perspectives and observations Tamarillos Craig Watson 50 Greenhouse John Thompson 54 Potatoes Christine Clouston 56 Process tomatoes Nigel Halpin 57 Process tomatoes Stuart Davis 58 Commercial Tim Herman 59Current season potato crops John Anderson 60Current research programme - entomology Peter Workman 65Current research programme - microbiology Andy Pitman 70IPM potential and Australian context Paul Horne 73Summary and life after today Gerhard Bester 79Conclusion Sonia Whiteman 79Informal Q&A session Gerhard Bester 80


Thanks to our sponsors:

Foreword

A workshop of this nature does not come together without a lot of help and interest from many people. A few deserve particular mention.

Joe Munyaneza volunteered to come to New Zealand to present the North American experience of psyllids and Liberibacter. In short order, the programme grew and the attendance list started to balloon, from an original estimate of 20-30, to over 80 actually attending. On hearing of these plans, Sonia Whiteman and Ron Gall, in spite of being fully involved in the main Congress planning, offered a venue and planning assistance. Without their endorsement and enthusiasm, my role would have been onerous.

Thanks also to our other overseas speakers: Gary Secor, who has been involved in Zebra Chip issues longer than anyone, Gerhard Bester who kindly offered the important role of summarising the day and then volunteered to lead the informal question and answer session, and Paul Horne who offered an interesting Australian perspective and insights into IPM practices of potatoes different to our New Zealand practices.

Thank you also to the rest of our speakers who found time to prepare a presentation in the busy season and to the many growers and research people who attended and participated so openly.

And finally, to our sponsors who offered without prompting.

For many of us, the eight months since the announcement in June 2008 of Liberibacter being shown to be associated with psyllid yellows, followed by documentation of Zebra Chip in New Zealand-grown potatoes and also associated with Liberibacter (in July 2008), have been a whirlwind of activity and learning. A few of us attended the ZC workshop in Dallas, Texas in December. Planning and executing research projects, trying to discover the likely differences between the US experience and what we can expect here, and planning information and response activities to support our growers, has been a dramatic experience in a normally more staid approach to research activity.

Just two weeks before this Workshop, we discovered evidence of Phytoplasma in some potato crops with foliar symptoms very similar to Liberibacter. While we know very little about this yet, we thought it useful to include some reference to what is known. Particular thanks to Lia Liefting, Joe Munyaneza and Gary Secor who modified their presentations at short notice.

From the early planning stages for this Workshop, I intended to ensure a record of the information would be available. My preference was to put together formal proceedings with the presentations in the form of papers. This was not to be – there is simply too much else happening and in some cases the presentation material will be published formally elsewhere. Rather than delay further, I felt it better to simply offer the presentation slides as is. Thank you to those who prepared written formats as these do make the content of presentations very much more accessible.

Warrick NelsonPlant & Food Research, Lincoln, New ZealandMay 2009


Welcome AddressWarrick NelsonPlant & Food Research, Lincoln

A big welcome to our speakers and to all of you for coming to participate in this workshop. I'm pleased to welcome so many from locally, but also so many from overseas. I note a number from the North Island, the West Island, the Eastern Pacific Island (north and south), the southern North Sea Island and the western Indian Ocean Island.

While our primary focus today is likely to be on potatoes, it is as well to note that we can learn from those battling with psyllids and Liberibacter in other solanaceous crops, for example tomatoes, capsicums, tamarillos, and even gardening and native plantings.

When we look at the difference in populations and resources between the USA and NZ, it is hard to believe that we few in New Zealand can make a difference. However, I believe we can offer a lot towards understanding of this insect/pathogen problem. The small size of our population and industry essentially forces even our specialists to take a far broader view and develop a wider range of expertise than is likely to occur in a bigger economy. We are used to developing co-operative links with others, especially in the research front. Our growers are seldom able to specialise exclusively in one crop, and their experiences are therefore taken from a broader range of crops and climates than might be the case in a larger country.

I've wanted to use this quote from Lord Rutherford for many years, and now is my chance. Research takes a lot of money to conduct. We need to ensure we use it wisely and effectively, but also not to treat them as interchangeable commodities.

I hope you will find the presentations today useful and I ask you to bring and share your experiences and expertise.

Before introducing our first speaker, I would like to raise four issues that may not arise otherwise or may derail more fruitful discussion.

Firstly, I would like to give a warning about single point bias. By this I mean a single point of view that takes on a greater relevance than perhaps is warranted. An example is the issue of insecticide resistance where a gene conferring a degree of resistance has been discovered in one population of the psyllids. However, the alternate view is demonstrated by another paper where farmer reports of widespread resistance are demonstrated to not be the case1. It is easy to see resistance when a spray application has not worked, but in this instance, is it not more likely that the psyllids are simply very hard to reach with standard spray equipment?

A second example of single point bias is the assumption that symptoms are caused by a toxin injected by the psyllid nymphs during feeding. This has become almost standard to report even though some of the very first reports last century strongly indicated some sort of pathogenic organism, a virus in the terminology of the day2.

1 Compare Liu & Trumble 2004 with Vega-Gutierrez et al 2008.2 Compare Binkley 1929 with Richards 1933 – Binkly referred to “viruliferous” psyllids and no transovarial transmission, while

Richards concluded a toxin was present, especially as plants recovered after removing psyllids. The view of Richard's prevailed.

Solanaceous crops – Psyllids & Liberibacter – March 2009 Page 1

“We haven’t got the money, so we have to think.”

Ernest Lord Rutherford

Secondly, taxonomy of 'our' Liberibacter is important for the wider scope of research and links to other areas of research. It is also important for us to refer clearly to the organism we are concerned about and therefore we need an unambiguous name. Unfortunately for us, not only are we dealing with a Candidatus status genus, but two species names are also being used. For the purposes of our discussion today, we need to merely recognise two names exist currently and hope that this anomaly will be resolved soon.

Thirdly, while we are not directly concerned with the citrus industry, there is a lot we can probably learn from their research. They have three species of Liberibacter associated with Huanglongbing (HLB)3, another yellows-type disease and vectored by two species of citrus psyllid. From their perspective, demonstration that tomato/potato psyllids can survive up to 10 days on citrus leaves indicates a potential route for infection for the solanaceous Liberibacter to spread to citrus. Equally, it offers a route for the reverse and to introduce the citrus Liberibacters into solanaceous crops. An extensive citrus and citrus psyllid survey in the USA has so far failed to find any solanaceous Liberibacter in citrus.

Fourthly, we recognise there are other areas of concern even if we are not explicitly covering them today. In particular, I refer to Maori interests, especially as regards Kumara and native plants of cultural significance such as poroporo. What else are these psyllids doing in our natural environment, and what impact can this environment have on the spread of pests and disease to crops? We will be covering briefly the recent discovery that a native Phytoplasma has jumped to potato crops where it appears to cause very similar symptoms as Liberibacter. Is there likely to be any impact on the native psyllids, especially those potentially impacted by controls aimed at the tomato/potato psyllid?

I encourage you to practice crowd-sourcing, where small units of information, when collated, take on a greater degree of significance and usefulness. An example is Wikipedia where Zebra Chip already has its own page. Together, we can accomplish far more than acting independently and I encourage you to participate fully today and as we progress our research plans and develop practical means of protecting our crops.

3 Also known as citrus greening.


“Candidatus Liberibacter psyllaurous/solanacearum” - the 16s rDNA fragments are identical. Number 834130 is from New Zealand (the bottom one), the others are from California.



ZC – North American contextGary SecorNorth Dakota State University








Psyllids – North American ExperienceJoe MunyanezaYakima Agricultural Research Lab, USDA-ARS
















Liberibacter and Phytoplasma – New Zealand contextLia LieftingPlant Health and Environment Laboratory, MAF Biosecurity New Zealand







Economic impacts, market access and preliminary observations of potato survey

Stephen OgdenMarket Access Solutionz







John Fletcher, Plant & Food Research, joined Stephen Ogden to answer questions about the survey and initial observations.


Phytoplasma – Columbia Basin Potato Purple TopJoe MunyanezaYakima Agricultural Research Lab, USDA-ARS












Tamarillo Growers

Craig Watson4

NZ Tamarillo Growers Association

Tamarillo is a solanaceous, subtropical tree crop, also known as tree tomato. The trees are free standing and have a rather soft wood. Their commerical life is 5-10 years. They are grown in Northland, Auckland, Bay of Plenty, Gisborne and Taranaki, with smaller plantings at Levin, Nelson and Karamea.

The industry is essentially 10 main growers, but about 100 smaller producers producing commercial crops. The industry has been moving towards a lower use of insecticides in general, and specifically towards pest specific and low toxicity products.

The main export market is Australia and this market was closed in June 2008 along with all other solanaceous crops. Tomato/potato psyllids were identified on some trees in South Auckland at this time, and have since been found on trees from Kaitaia to Opotiki. Existing spray programmes have not controlled psyllid infestations. Liberibacter in tamarillo was first confirmed from trees in Whangarei in December 2008 and symptoms appear to become significant as the crop load increases through the season.

4 Presented by Warrick Nelson. Craig can be contacted through www.tamarillo.com


Early symptoms are cupping and pink colouration of new growth.

http://www.tamarillo.com/


Mature trees show yellowing of leaves and eventually peripheral burning leading to leaf drop, branch dieback and tree death over 2-4 months. This often looks similar to phytophthora infection, but the trees remain firm in the ground while with phytophthora the root breakdown results in trees becoming unstable in the ground.


Symptoms can be restricted to particular branches. The back half of this tree has growth nearly normal with fruit set wile the front half has smaller leaves and no fruiting.

If shoots are produced, they are often multiple shoots from a single bud that remain thin with small leaves and no fruit trusses develop. The four shoots in the centre of the picture is a good example. The leaves are only 6-10cm long, about half normal size, although leaf colour is normal.

Pruned trees show poor bud break and tiny shoots with small leaves. This progresses to shoot dieback and tree death over 1-4 months.

Psyllid behaviour on tamarillo

The psyllids appear to prefer the underside of newly mature leaves. Even in a heavy infestation, they seldom occur at greater than three per leaf. They appear to avoid leaves with obvious Liberibacter symptoms.

The warmest part of the block is populated first. Infestation is not even and blocks with heavy infestation can be adjacent to clean blocks. As the trees are subtropical, it is reasonable to expect the psyllids to overwinter on them.

Growers have found them to be difficult to control, even using chemicals reputed to be effective and are now relying on spraying contact insecticides. Calypso, Chess, Success Naturalyte, Applaud, Oberon and Coragen do not control TPP on tamarillo at label rates. Contact inseciticdes such as Nuvos, Decis and Avid (although Avid has translaminar activity it appears to have no residual effect on TPP when sprayed as a contact insecticide) have shown greater control. However, routine spraying is unacceptable to growers or the marketplace and alternatives are urgently needed.

The Association is keen to work with other crop growers should the SFF funding grant be successful and has committed research funding towards the goals of this programme. Growers are being encouraged to be vigilent in their monitoring and identification of the psyllids and Liberibacter symptoms. We are still awaiting the outcome of Pest Risk Analysis by Biosecurity Australia as the Australian market is still closed for exports.

The psyllid/Liberibacter combination can be expected to destroy garden plantings of tamarillo, as well as severly limit the viability of lowinput/organic systems. The symptoms on trees are debilitating and progress to tree death.


Industry perspectives and observations – greenhousesJohn ThompsonBioforce



Industry perspectives and observations – potatoesChristine CloustonMcCains


Industry perspectives and observations – process tomatoesNigel HalpinHeinz Watties


Stuart Davis, Leaderbrand Produce, also spoke on their experiences in field-grown tomatoes for processing.


Industry perspectives and observations – CommercialTim HermanFruitfed


Current season potato cropsJohn AndersonPlant & Food Research, Pukekohe

AbstractThe potato/tomato psyllid (PTP) is a potentially significant new pest for the New Zealand potato

industry. It causes significant yield losses and crop damage in North America, particularly in the southern states of the USA. Tuber symptoms include zebra stripe (a condition similar to internal fleck, which in turn causes distinct dark stripes in crisps), misshapen tubers with reduced size, premature sprouting with weak hair sprouts, shorter stolons, and rough skin. Numbers of small tubers are often increased. Tops are generally smaller with yellowing or purpling and can develop a blackened scorched appearance before premature collapse.

New Zealand has ideal temperate conditions for PTP. It has caused considerable losses to the potato breeding programme at Pukekohe in 2008, with lower trial yields and quality and greatly reduced selection frequency from the seedling populations. In 2009 with a much more intensive spray programme yields have not been affected but significant quality problems with zebra stripe symptoms in both raw and fried tubers has occurred. It has the potential to be a serious problem for the wider potato industry.

Growers may have been protected from serious psyllid damage in 2008 by regular applications of insecticide to control tuber moth but with increased and more widespread PTP populations widespread quality problems are likely throughout New Zealand. The problems associated with PTP are likely to be much greater than potato cyst nematode which caused huge disruption to the New Zealand potato industry after its discovery in New Zealand in 1972.

IntroductionThe potato/tomato psyllid (Bactericera cockerelli) was first identified in glasshouses in New Zealand in the Auckland region in April 2006 and was identified in the field at the Pukekohe Research Centre in February 2007 (Peter Workman, pers. comm.).

The psyllid was one of the major topics of discussion at the Potato Association of America (PAA) meeting that I attended in Idaho Falls in August 2007.

This report outlines important findings from the 2007/08 and early season trials 2008/9 potato breeding trials at Pukekohe, which were severely affected by symptoms attributable to PTP infestation.

Effect of psyllids on Pukekohe potato breeding programmeSeedlings & Early generation trialsAt Pukekohe between 10,000 and 18,000 seedlings are grown from true seed each year, transplanted into the field in early December and harvested individually in late March. Typically 10-15% of seedlings are selected each year. In the 2006/07 year, changes were made in the herbicide regime within the seedling block and seedling performance was very poor with only 4.8% of seedlings being selected. The poor performance was initially put down to herbicide damage. In 2007/08 we reverted to previous herbicide practices and early establishment and growth of the seedlings was good. However, they generally failed to continue growing well and at harvest, even after relaxed selection standards, only 2.8% were selected. The only possible reason we can see for this poor performance is psyllid damage (see below), and in retrospect the poor performance the previous year was probably at least partly due to the effect of the psyllid.

In 2008/9 an intensive insecticide programme was applied. Yields were good, but a significant number of seedlings, often with good yields were rejected because of zebra stripe symptoms visible in the field. Despite this 12% were selected, within the normal range.


The first clonal (C1) four tuber plots grown from the 2007/8 seedlings grew remarkably well considering the very poor seed tubers that were planted. There was a low transmission (about 5%) of secondary liberibacter symptoms from the seedling seed tubers.

Regional potato breeding trialsAt Pukekohe there are three major regional breeding trials, the early trials harvested immediately before Christmas, the early-main trials normally harvested in February-March, and the main-crop trials harvested in May-June.

In the 2007/08 season, early trial performance was fine with yields and overall quality of the potatoes being good and well within the expected range. The entomologists were detecting low psyllid populations in the field from late December. Yields of the early-main crop harvested at the end of February were around half to two-thirds of expected levels with slightly lower dry matter levels than expected, but apart from slightly smaller tuber size, quality was as expected. A delayed planting due to wet weather may have contributed in part to the lower yield of this trial, but psyllid infestation was also likely to have been a major contributor.


2007/08 season main crop early April. Tops blackened suddenly.

However, in the main-crop trials harvested in late May, tuber yields and dry matter levels were both extremely poor, both being substantially lower than in the early-main trial for every line common to both trials. Nadine was the only line with a dry matter level approaching normally accepted standards, having a dry matter level in the top 20% whereas normally it would be expected to be near the lowest dry matter. Tuber quality was generally extremely poor with small size, a heel or stolon attachment common, irregular shape, excessive sprouting and in some tubers indications of symptoms of zebra stripe. Tuber numbers were high, with many small marbles produced by many lines. Fry colour (Agtron score) was also darker in all lines, and considerably darker in some, suggesting much higher reducing sugar levels. All of these symptoms (except for the lower dry matter) are recorded as typical symptoms of psyllid infestation in the USA. Vigour was slightly lower than expected when the trials were scored for maturity in mid March, and the tops of all lines blackened off in early April about the time when the shorter maturing lines would have died off. Yield and quality data for Pukekohe trials in 2007 and 2008 are presented in Table 1.

MAF Biosecurity took samples from the trials that had symptoms of zebra stripe and confirmed the isolation of the bacterium Candidatus liberibacter, the first time this had been recognised in potatoes (Liefting et al., 2008).

We routinely used much lower levels of insecticide than most growers. We are less concerned with a low level of tuber moth damage as we do not market our potatoes and are looking for an indication of resistance. The only insecticide applied was two applications of Karate, a synthetic


Extremely high psyllid nymph infestation on leaves.

pyrethroid. I was taken by surprise at the serious effect that psyllids had on the 2007/8 trials and decided to use a much more intensive insecticide programme aimed directly at the psyllid in 2008/9.

In the 2008/9 season early trials harvested in December again had satisfactory yield and quality. Regular weekly insecticide applications commenced in early December when the number of adult PTP caught in sticky traps exceeded one PTP/trap/week. Despite this numbers of adults caught per trap reached 100/week but the numbers of nymphs on the plants remained low. The first four weeks insecticide applications were of imidacloprid which work by Walker & Berry (2008) suggests may have low efficacy on PTM, at least on nymphs.

The early main trials harvested in late February had generally satisfactory yields and often high dry matter levels but there were differences between the levels of zebra stripe in raw tubers from moderately severe to complete absence. Fry tests showed a level of zebra chip generally higher than expected from the symptoms in the raw tuber.


Variation in ZC expression in tubers.

Cultivar

Total yield t/haMarketable yield

t/haAverage

dry matter %

Tuber size1 (tiny) – 9

(huge)

General impression1 (v bad) – 9 (v

good)Fry colour

40 acceptable

2007 2008 2007 2008 2007 2008 2007 2008 2007 2008 2007 2008

Moonlight 52.1 20.8 49.1 16.9 16.7 11.6 6 4 6 3 42 40

Rua 42.9 17.0 38.5 10.4 17.6 12.8 5 3 5 2 46 32

Agria 50.7 30.0 42.8 26.2 18.3 13.6 5 4 6 4 48 40

Allura 58.5 20.7 51.2 10.9 17.3 10.7 5 3 6 2 40 32

Bondi 57.2 26.9 52.5 21.6 18.3 12.8 6 4 8 4 40 34

Fianna 37.2 27.4 30.2 18.7 20.0 16.0 5 3 5 4 48 44

Golden Miracle 52.2 19.8 44.4 14.6 18.8 13.6 4 3 5 2 50 40

I Hardy 59.2 25.2 47.0 15.9 13.5 9.0 5 4 3 1 30 25

Nadine 38.0 24.4 30.7 17.4 16.6 14.5 3 3 6 4 30 28

R Burbank 38.9 26.5 33.2 21.4 18.9 14.5 4 3 4 3 50 38

Crop20 43.9 19.3 40.6 10.5 18.1 13.5 5 2 6 2 42 34

Table 1: Liberibacter and psyllid effects on potato crops.

ConclusionPTP and the associated liberibacter conditions have had a large detrimental effect on the Plant & Food Research potato breeding trials at Pukekohe since the first identification of the PTP on the Pukekohe Research Centre in February 2007.

They are major concern for the New Zealand potato industry. Within a year of my starting as a potato researcher in 1971 the discovery of potato cyst nematode caused major concern and disruption to the New Zealand potato industry for many years. Because of its ability to spread rapidly, cause drastic reductions in yield and massive quality problems even when yields are acceptable, I consider the PTP to be a far bigger crisis than PCN5 ever was.

One of the consistent messages of the World Potato Congress was the potential increasing importance of the potato in adequately feeding the world as population levels head to a peak of nine billion people. Based on the potential devastation the PTP has been shown to cause, this hope could be severely compromised if it became more widely established throughout the world.

ReferencesLiefting L W, Perez-Egusquiza Z C, Clover G R C, Anderson J A D 2008. A new ‘Candidatus

liberibacter’ species in Solanum tuberosum in New Zealand. Plant Disease 92 (10): 1474Walker, M, Berry N 2009. Insecticides have potential for tomato/potato psyllid control. Grower

(April) 64 (3): 27-28.www.panhandle.unl.edu/potato/html/potato psyllid.htm Potato Psyllid. Potato Education Guide.

5 Potato cyst nematode


http://www.panhandle.unl.edu/potato/html/potato%20psyllid.htm

Current research programme - entomologyPeter WorkmanPlant & Food Research






Current research programme - microbiologyAndy PitmanPlant & Food Research




IPM in Australian potato crops and the threat from potato psyllid.

Paul Horne and Jessica PageIPM Technologies Pty Ltd, PO Box 560, Hurstbridge, Australia [email protected]

AbstractWe describe here the IPM strategy that we developed for Australian potato crops and the pests with

which it must deal. The potential impact of potato psyllid on this IPM strategy is a serious concern and has the potential to destroy the strategy that is currently in place, and that some growers have used successfully for over 13 years. The main foliar pests that we must deal with are potato tuber moth (PTM) (Phthorimaea operculella), several other caterpillar species, and aphid species including green peach aphid (Myzus persicae).

IntroductionIPM requires an integrated set of control options for all pests, both major and minor, that are encountered in any crop. Potato crops are no different and there are beneficial species that occur in potato crops worldwide, cultural options that are available and also selective pesticide options. We describe here how an IPM approach to potato pests was developed in Australian crops. Our work on potato tuber moth (PTM) began in 1986 when organochlorine insecticides (including DDT and dieldrin) were still permitted for use on some potato crops in Australia, and use of organophosphates and synthetic pyrethroid insecticides were standard practice.

There is an extensive literature relating to PTM and its biological control and Australian work prior

to ours include papers by Briese (1981) and Callan (1974). Studies that we have carried out on the


Potato tuber moth and damage to potato crops.

mailto:[email protected]

relative importance of different species of parasitoids have shown that there are established populations of parasitoids of PTM and that these vary according to location (Horne 1990). The objective of our studies was the development of an IPM system for all potato pests. The papers published on potato IPM topics by Paul Horne and co-workers is summarised by Horne and Page (2008).

Materials and MethodsAs in any IPM strategy, the primary controls are biological and cultural, supported by selective pesticides, only when necessary. Broad-spectrum insecticides such as synthetic pyrethroids, organophosphates, and others must be avoided as foliar sprays. The major pests that are encountered in Australian potato crops are PTM, Helicoverpa armigera (Hubner), green peach aphid (Myzus persicae (Sulzer)), potato aphid (Macrosiphum euphorbiae (Thomas)), onion thrips (Thrips tabaci Lindeman), tomato thrips (Frankliniella schultzei (Trybom), western flower thrips (F. occidentalis Pergande), whitefringed weevil (Naupactus leucoloma) (all exotic species to Australia), looper caterpillars (Chrysodeixus argentifera (Guenee) and C. eriosoma (Doubleday)) and potato wireworm (Hapatesus hirtus Candeze), but there are many other minor, local or infrequent pests. Potato wireworm in Australia is different to species of potato wireworm elsewhere in the world and has a very different life-history (Horne & Horne 1991). A range of native and introduced natural enemies of these pests are used in IPM strategies. The most important of these are native predators: damsel bugs (Nabis kinbergii Reuter), pentatomid bugs (Oechalia schellembergii (Guerin-Meneville), brown lacewings (Micromus tasmaniae Walker), ladybird beetles (Coccinella transversalis Fabricius, Hippodamia variegata (Goeze) and Harmonia conformis (Boisduval) and red and blue beetles (Dicranolaius bellulus (Guerin-Meneville)). There are many parasitoids of the pests, and these include native species that attack the native pests, and also introduced species such as Orgilus lepidus Muesebeck, Apanteles subandinus Blanchard and Copidosoma koehleri Annecke and Mynhardt that parasitise PTM.

Cultural controls are equally as important as the biological controls and include soil preparation and management, irrigation, location of plantings, seed source and variety selection. Cultural controls such as rolling, watering, and harvesting early or hilling were more important options proposed than spraying insecticides. A major cultural control that we needed to implement was a good “hill” made of fine soil (not cloddy soil) which provided good soil cover over developing tubers. Soil management is a critical component of our IPM strategy.

Selective insecticides such as Bacillus thuringiensis sp. kurstaki (BT) sprays are sometimes used, but the typical control of pests is achieved by biological and cultural means. Growers who have changed from conventional control based on insecticides to an IPM approach have made significant


Orgilus lepidus

reductions in pesticide use, with associated savings (eg from 7 insecticides per crop to none (O’Sullivan & Horne 2000). Growers successfully using IPM include those producing certified seed, crisping, processing, ware and organic crops, and some growers have been using the strategy for over 13 years.

The approach we took required monitoring for all pests that occurred during the life of the crops and recommending actions that would control that pest without interfering with control of other pests. That is, applying actions that would not kill biological control agents for other potato pests. All monitoring and advice reported here concerns commercial farms, not plot trials or small trial results within commercial crops.

Results and DiscussionWhen we commenced research on PTM in 1986 there was almost total reliance on chemical insecticides as the basis for control of all pests. This appears to be the current situation in other countries such as the USA and UK now. The potato industry had very little knowledge of biological control agents and how these could potentially be used in an IPM strategy. Although there was interest from the potato industry there was also scepticism and a need for both scientific information and on-farm demonstration of IPM. This situation is one that we have encountered in a range of horticultural and broad-acre cropping industries and our approach to dealing with it is by simultaneously gathering entomological information and providing commercial demonstrations of IPM (Horne, Page & Nicholson, 2008).

We were able to show that parasitoids of PTM and aphids were present in all areas where potatoes were grown and that they exerted considerable control pressure on these two key pests. The main parasitoid recovered from samples was the larval parasitoid Orgilus lepidus, followed in importance by another larval parasitoid Apanteles subandinus. The egg-larval polyembryonic parasitoid Copidosoma koehleri was found from most locations but was far less abundant than the larval parasitoids (Horne 1990).

Suddenly we needed to be aware of all pesticide inputs (and not only for PTM management) and we realised that we had totally ignored the potential biological control provided by predators (as well as parasitoids) and that the cultural controls of hilling and irrigation were at least as important as parasitoids of PTM. We now had to deal with all pests of potatoes in a compatible way, not just promote the parasitoids of PTM. This was entirely possible, as there are IPM compatible options for all aphids, caterpillar and other pests of potatoes in Australia (Horne 2000). Table 1 provides an example of the integration of several options in a compatible way. To assist growers and others in recognizing the beneficial species as well as the pests a guidebook was prepared which was


Copidosoma, and parasitizing PTM larvae on left.

distributed to all potato growers in Australia (Horne, DeBoer & Crawford 2002).

In Australia there is a problem with tomato spotted wilt virus in potatoes and this is vectored by several species of thrips; onion thrips (Thrips tabaci Lindeman), tomato thrips (Frankliniella schultzei (Trybom) and western flower thrips (F. occidentalis Pergande). Control of these pests without recourse to broad-spectrum insecticides is essential to overall control of pests, including PTM (Horne & Wilson 2000). Obviously, broad-spectrum foliar sprays of insecticides targeting thrips will have massive detrimental effects on the biological control of potato moth and aphids (and aphid vectored diseases). Growers using IPM understand that they have beneficial species that help to control key pests and also avoid the development of secondary pests.

Our observations show that broad-spectrum insecticides applied to control pests such as caterpillars can cause aphid flare. We believe that this is a general principle that can be extrapolated to many situations. Control of potato psyllid (Bactericera cockerelli ) with foliar applied insecticides would cause interference with the biological control of the other main pests of potatoes in Australia, and so destroy the main elements of an IPM strategy. There are known predators of potato psyllid outside Australia that belong to the same groups as those native Australian species that are already important in control of other potato pests. It is not known how effective these native species will be in controlling potato psyllid and this needs to be studied as soon as possible.

ConclusionOne of the main issues that we had to deal with in Australia was the integration of several pest issues (e.g. potato moth and aphids and looper caterpillars) and the recognition that an inappropriate spray for one would disrupt control of other pests. This apparently simple issue is a stumbling block for IPM adoption in a range of horticultural and broad-acre crops in which we work. We need to develop biological and cultural control options for potato psyllid so that potato farmers using IPM can continue to do so.


Table 1: An example of a typical IPM strategy for potatoes integrating several control options

Pest Beneficial Cultural Control Pesticide supportPTM O. lepidus

A. subandinusC. koehleri

Soil managementIrrigation

Spray after senescence

Green Peach Aphid Parasitic waspsLadybird beetles

Weed control Pirimicarb

Other Aphids Parasitic waspsLadybird beetles

Weed control Pirimicarb

Heliothis Damsel bugsParasitoids

- NPV, BT

Loopers Damsel bugsParasitoids

- BT

Whitefringed weevil

Carabidae Avoid infested areas Insecticide before planting

Potato Wireworm Carabidae Avoid infested areas Insecticide before planting, seed dressing

AcknowledgementsWe would like to thank the many potato growers who have collaborated with us for many years. In addition we would like to acknowledge the support of AusVeg and Horticulture Australia Limited (HAL) (formerly HRDC) with several projects on potato pests.

ReferencesBriese, D.T. (1981). The incidence of parasitism and disease in field populations of the potato moth

Phthorimaea operculella (Zeller) in Australia. Journal of the Australian Entomological Society 20: 319 – 326.

Callan, E.M. (1974). Changing status of parasites of potato tuber moth Phthorimaea operculella (Lepidoptera: Gelechiidae) in Australia. Entomophaga19: 97 – 101.

Horne, P.A. (1990). The influence of introduced parasitoids on potato moth Phthorimaea opeculella (Zeller) in Victoria, Australia. Bulletin of entomological Research 80:159-163.

Horne, P.A. (2000). Integrated Pest Management (IPM) in use - Overview. Proceeding of the Potatoes 2000 Conference, pp. 89-92. Adelaide.

Horne, P.A. and Horne, J.A. (1991). The biology and control of Hapatesus hirtus Candeze (Coleoptera: Elateridae) in Victoria. Australian Journal of Agricultural Research 42:827-34

Horne, P.A.; De Boer, R. and Crawford. D.J. (2002). Insects and diseases of potato crops. Melbourne University Press. 80pp.

Horne, P. and Page J. (2008). Integrated Pest Management dealing with potato tuber moth and all other pests in Australian potato crops. In: Kroschel J and L Lacey (eds) Integrated Pest Management for the Potato Tuber Moth, Phthorimaea operculella Zeller – a Potato Pest of Global Importance. Tropical Agriculture 20, Advances in Crop


Impact of parasitoids in potato crops.

Research 10. Margraf Publishers, Weikersheim, Germany, 111-117.Horne, P.A.; Page, J. and Nicholson, C. (2008) When will IPM strategies be adopted? An example

of development and implementation of IPM strategies in cropping systems. Australian Journal of Experimental Agriculture, 48:1601 - 1607.

Horne, P.A. and Wilson, C. (2000). Thrips and tomato spotted wilt virus – on the increase: situation report. Proceeding of the Potatoes 2000 Conference, pp. 103 – 106.

O’Sullivan, P. and Horne, P.A. (2000). Using Integrated Pest Management (IPM) on farm. Proceeding of the Potatoes 2000 Conference, pp. 93-96. Adelaide.


Summary and life after todayGerhard BesterFritolay

During his summary6 of the key points of the Workshop, Gerhard also noted that interpretation of sticky trap results is not yet clear, in particular to develop action thresholds.

He also invited participants to attend the next ZC conference in December. This conference will include citrus interests.

He applauded and encouraged further collaboration, especially in terms of sharing chemical effectiveness information, resolving market access issues, and development of beneficials programmes. In particular, he noted that US growers had not focused on IPM effects of their psyllid control treatments.

Gerhard offered to lead an informal question and answer session for those who were interested after the formal conclusion of the Workshop.

ConclusionSonia WhitemanHorticulture New Zealand

6 A few notes made by me, Warrick Nelson, during his speach.


Informal Q&A session

A few notes made by me, Warrick Nelson, during the session.7

Gary Secor Necrosis of the phloem in medullary rays and the pink “belly button” are diagnostic for ZC.

Gary Secor Some pictures of fried crisps/chips show slight darkening, this is related to frying young tubers and is an artifact called oil clearing.

Joe Munyaneza Psyllids on eggplants – the plants last a long time and show no symptoms.Joe Munyaneza Non-ZC inducing psyllids – foliar symptoms on potatoes look very like ZC, but

tubers are clear. The plants survive with symptoms for a long time, and removing the psyllids results in healthy regrowth.

Lia Liefting Bidens – first note of this Liberibacter outside Solanaceae. The plant was alongside a commercial potato crop – species unknown.

Lia Liefting Seed transmission – tests were done 5-10 weeks after germination. 50 plants have been kept for longer to see whether any symptoms arise. (Note – tomato and tamarillo seed, not potato. WN).

Lia Liefting The Phytoplasma sample was received in January. Potato symptoms do not always show purpling, and sometimes aerial tubers form. Fresh tubers show no symptoms, but fry even darker than with Liberibacter. Some samples were positive for both bacteria.

Stephen Ogden/John Fletcher

No psyllids found on potato crops in Canterbury, although some have been caught in yellow sticky traps.

John Thompson Some greenhouse crops are still being severely affected. Growers generally remove affected plants. Growers need to know whether the symptoms are psyllid feeding damage or Liberibacter before they remove plants.

John Thompson Bumble bees have been used to carry biocontrol agents to crops.Essential oils are also being investigated – they appear to inhibit psyllid egg laying.

Nigel Halpin Processing tomato fruits are soft and low in brix resulting in a poor yield through the factory.

Gerhard Bester The stolbur Phytoplasma in Eastern Europe gives the same ZC symptoms in fried chips. They do not have Liberibacter. ZC is therefore a tuber symptom and can arise from more than one bacterium.US growers also have some export issues arising from Liberibacter.

Gerhard Bester Aphoil – a mineral oil, appears to work well. Some growers use it in back to back applications with other chemicals.IPM aspects – US potato experience has not yet taken IPM aspects into account and they will be watching NZ/Australian developments.

7 These were not verbatim notes and in some cases followed extensive discussion by many participants around the topic. I have attempted to attribute the source, but in some cases there was very extensive discussion.


Phytoplasma discussion

• Scouts report symptoms spread across fields, moving within 7 days of first report. It appears to take 20 days to get infection and then 20 days to first symptoms, ie 40 days from emergence. The group was about evenly split between being convinced Phytoplasma was likely to be psyllid vectored, and those who expect a leafhopper to be the culprit.

• Joe noted that we will need to document and test all insects present from plant emergence, not just when symptoms appear. Growers had not noted leafhoppers on their crops in the Columbia Basin. The leafhoppers acquire Phytoplasma from other plants and then transmit it to potatoes.

• Is hollow heart associated with Phytoplasma? In the US, occasional hollow heart is noted, but not associated with Phytoplasma.

• Purple top-like symptoms have occasionally been seen for years, just not across whole fields. Was the serious drought and psyllid infestation a factor?

• Eastern Europe stolbur Phytoplasma is vectored by a plant hopper of unknown species. Little is known of their biology and the other plants acting as a source for Phytoplasma. Stolbur phytoplasmas are common across a wide range of crops and weeds.

• Jerusalem cherry – had psyllid nymphs, tested positive for Phytoplasma and negative for Liberibacter.


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Solanaceous crops, Psyllids \u0026 Liberibacter