Project Title:Protected herbs: Control of glasshouse whitefly and
leafhoppers within IPM programmes
Project Number:PC 178
Project Leader:Jude Bennison, ADAS Boxworth
Report:Final Report, March 2001
Previous reports:None (this project was for one year only)
Key workers:Jude Bennison, ADAS Boxworth (Project management,
visiting five nurseries in survey, provision of report)
Mike Lole, ADAS Wolverhampton (identification of pests and parasitoids and visiting one nursery in survey)
Roger Umpelby, ADAS Rosemaund (visiting two nurseries in survey)
Heather Maher and Kerry Maulden, ADAS Boxworth (insect cultures and laboratory work)
Location of Project:8 commercial herb nurseries and:
ADAS Boxworth
Boxworth
Cambridge
CB3 8NN
Tel: 01954 268225
Fax: 01954 268268
email:
Whilst reports issued under the auspices of the HDC are prepared from the best available information, neither the authors not the HDC can accept any responsibility for inaccuracy or liability for loss, damage or injury from the application of any concept or procedure discussed.
The contents of this publication are strictly private to HDC members. No part of this publication may be copied or reproduced in any form or by any means without prior written permission of the Horticultural Development Council.
Project Co-ordinators: Dr Laurie Reed
Yorkstock
Clifford Moor Road
Clifford
Wetherby
North Yorks
LS23 6LD
Tel: 01937 541387
Fax: 01937 541066
Dr Paul Sopp
Fargro Ltd.
Toddington Lane
Littlehampton
West Sussex
BN17 7RP
Tel: 01903 721591
Fax: 01903 730737
Date Project Commenced:1 June 2000
Date Project Completed:30 April 2001
Key Words:leafhopper, Eupteryx melissae, Anagrus atomus, glasshouse whitefly, Trialeurodes vaporariorum, Encarsia formosa, willow-carrot aphid, Cavariella aegopodii, lacewing, Chrysoperla carnea, Aphidoletes aphidimyza, herbs, sage, Salvia officinalis, Eradicoat, fatty acids, Savona, heptenophos, Hostaquick, nicotine, petroleum oil, Verticillium lecanii, Mycotal, Beauveria bassiana, buprofezin, Applaud, pymetrozine, Chess, pirimicarb, Aphox
The results and conclusions in this report are based on an investigation conducted over one year. The conditions under which the experiment was carried out and the results obtained have been reported with detail and accuracy. However because of the biological nature of the work it must be borne in mind that different circumstances and conditions could produce different results. Therefore, care must be taken with interpretation of the results especially if they are used as the basis for commercial product recommendations.
PRINCIPAL WORKERS
J A Bennison, Senior Research Entomologist, ADAS Boxworth (Project Leader and author of report)
M J Lole, Senior Research Entomologist, ADAS Wolverhampton
R A Umpelby, Senior Research Entomologist, ADAS Rosemaund
H M Maher, Senior Scientific Officer, ADAS Boxworth
K A Maulden, Senior Scientific Officer, ADAS Boxworth
AUTHENTICATION
I declare that this work was done under my supervision according to the procedures described herein and that this report represents a true and accurate record of the results obtained.
...... J A BENNISON
Project Leader
Date......
Report authorised by: ......
Dr M Heath
Manager, ADAS Boxworth
Date......
.
CONTENTS
Page no.PRACTICAL SECTION FOR GROWERS / 1
Commercial benefits of the project / 1
Background and objectives / 1
Summary of results and conclusions / 1
Action points for growers / 3
Anticipated practical and financial benefits / 4
SCIENCE SECTION / 5
INTRODUCTION / 5
Objective 1: Identification of leafhopper species
/ 7- Materials and Methods / 7
- Results and Discussion / 7
- Conclusions / 11
Objective 2: Identification of naturally occurring leafhopper parasitoids and potential for commercial use / 11
- Materials and Methods / 11
- Results and Discussion / 12
- Conclusions / 16
Objective 3: Herb species on which Encarsia formosa is poor or unreliable and possible factors affecting control / 16
- Materials and Methods / 16
- Results and Discussion / 17
- Conclusions / 25
Objective 4: Collation of information on the efficacy of currently available IPM-compatible pesticides against leafhoppers and glasshouse whitefly / 26
- Materials and Methods / 26
- Results and Discussion / 26
- Conclusions / 38
Objective 5: Incidence of willow-carrot aphid and assessment of whether research on biological control of the pest is justified / 41
- Materials and Methods / 41
- Results and Discussion / 41
- Conclusions / 42
Objective 6: Production of factsheet
/ 43OVERALL CONCLUSIONS FROM THE PROJECT / 43
TECHNOLOGY TRANSFER / 44
RECOMMENDATIONS FOR FUTURE RESEARCH / 44
REFERENCES / 47
APPENDICES / 52
2001 Horticultural Development Council
PRACTICAL SECTION FOR GROWERS
Commercial benefits of the project
The project identified the main species of leafhopper damaging protected herbs and a naturally-occurring egg parasitoid which may have potential for commercial rearing and use within Integrated Pest Management (IPM). Possible reasons for unreliable biological control of glasshouse whitefly on protected herbs by Encarsia formosa were identified. Information was collated on the efficacy of currently available IPM-compatible pesticides against both pests and the potential for additional pesticides for use on herbs was identified. The incidence of willow-carrot aphids on protected herbs was estimated and control measures within IPM identified.
Background and objectives
Growers of protected herbs are experiencing difficulties in controlling leafhoppers and glasshouse whitefly within IPM programmes. There is no biological control agent available for the main leafhopper species occurring on herbs and the most effective pesticide, Hostaquick (heptenophos), was withdrawn on 20 April 2001. Control of glasshouse whitefly on herbs with the parasitoid Encarsia formosa is unreliable and there is no available fully effective pesticide. Due to the low or ‘zero’ retail tolerance for pests or damage on culinary herbs, effective control is essential. This project aimed to confirm the main species of leafhopper damaging protected herbs, identify the herb species on which current biological control methods for glasshouse whitefly are unreliable, estimate the incidence of willow-carrot aphid on susceptible herbs, and identify whether research is justified to investigate the potential of candidate biological control agents against each pest. Guidelines will be given to growers on currently available methods for control of leafhopper and glasshouse whitefly within IPM on herbs.
Summary of results and conclusions
Identification of leafhopper species
Eight herb nurseries using IPM were visited between June and October 2000. Leafhopper was a problem on six nurseries and confirmed as the chrysanthemum leafhopper (often known as the ‘sage leafhopper’), Eupteryx melissae. The potato leafhopper, Euperyx aurata was damaging spearmint on one nursery. Sages were the main species damaged by E. melissae but balm, basil, bergamot, French lavender, mints, marjorams, oregano, rosemary and thymes were also affected. Plant losses ranged from 1-50% and significant costs were incurred in time spent spraying, picking off damaged leaves or selecting plants for cutting.
Identification of leafhopper parasitoids
Naturally-occurring leafhopper egg parasitoids were found on herbs from four nurseries and were confirmed as belonging to the Anagrus atomus species group. A. atomus is commercially available for the control of glasshouse leafhopper, Hauptidia maroccana, but the parasitoid is reported not to attack E. melissae. The A. atomus strain found on the herb nurseries is likely to be adapted to E. melissae and may have potential for commercial rearing and use within IPM. A laboratory culture of the parasitoid was established at ADAS Boxworth, for further research if agreed.
Incidence of glasshouse whitefly and control by Encarsia formosa
Glasshouse whitefly was a severe problem on two of the eight nurseries and had been a problem in the past on another two nurseries. Problem herbs included sages, lemon verbena, mints, marjorams, bergamot, basil, balms and rue. Infested stock plants were thought to be a frequent source of the pest. Control by E. formosa was variable and seemed more successful where the parasitoids were released weekly, starting before whitefly was seen. This could be allowing ‘overkill’ of whitefly, when the adult E. formosa act more like predators than parasitoids, by ‘stinging’ and killing the young scales before they reach the preferred stage for parasitism. Such ‘host-feeding’ is likely to be more important than parasitism on herbs due to the low market tolerance of whitefly. Possible reasons for unreliable control by E. formosa include introducing too few parasitoids too late, low temperatures, plant characteristics such as hairy leaves or strong scent inhibiting or repelling E. formosa and the short herb production period meaning plants are sold before parasitised scales are visible or have hatched.
Efficacy of currently available IPM-compatible pesticides against leafhopper and glasshouse whitefly
There are very few IPM-compatible pesticides approved for use on protected herbs with efficacy against leafhopper and glasshouse whitefly. This is limiting effective IPM and reducing plant quality and marketability.
Leafhopper: Most growers have relied on Hostaquick2 (heptenophos) but approval was revoked on 20 April 2001. Nicotine 40% shreds1, Nico-Soap2, No-fid2, XL-All Insecticide2 or XL-All Nicotine2 should give some control but repeated applications are needed and this disrupts IPM. Savona2 (fatty acids) gives partial control but the product may only be used once per crop on herbs. Eradicoat3 (plant and vegetable oil extracts) and Hortichem Spraying Oil3 (petroleum oil) may give some control but no data is yet available on efficacy against leafhopper or safety to herbs with either product. Mycotal2 (Verticillium lecanii) has not been tested against leafhopper.
Glasshouse whitefly: Savona should control both adults and scale stages if good coverage of the undersides of the leaves is achieved, but repeated sprays are needed and Savona may only be used once per crop on herbs. Eradicoat should give control of whitefly pupae and some control of younger scale stages. Spraying oil has not been tested against glasshouse whitefly, although it has been shown to be effective against the tobacco whitefly, Bemisia tabaci. Nicotine products give only limited control of whitefly adults. Mycotal controls whiteflies if temperatures exceed 18C and RH% exceeds 80% but these conditions are likely to be met only in herb propagation houses.
1 On-label approval for use on protected herbs
2 On-label approval for use on lettuce, thus can be used off-label at grower’s own risk under the
Revised Long Term Arrangements for Extension of Use (2000).
3 Acts by physical means only so not subject to pesticide regulations.
Incidence and control of willow-carrot aphid
Willow-carrot aphid was confirmed on four nurseries, on parsley, chervil or coriander. The pest was only a problem at one site where the likely source was an adjacent carrot field. Parasitoids did not attack willow-carrot aphid but lacewing larvae, Chrysoperla carnea and predatory midge larvae, Aphidoletes aphidimyza eventually gave control. No research on biological control of this pest on herbs is recommended at present.
Factsheet for growers
A factsheet has been prepared and will be distributed by HDC.
Action points for growers
This project aimed to identify and quantify the problems of controlling glasshouse whitefly and leafhopper in protected herb crops using IPM programmes. Further measures involving R&D and pesticide approvals will be needed to address the problems identified. In the meantime the following guidelines should be followed:
- Minimise leafhopper and whitefly carry-over by clean-up of unmarketable plants and by weed control in and around glasshouses/tunnels. Keep stock plants in a separate structure if practical and keep them as free from both pests as possible.
- Aim for whitefly ‘overkill’ by releasing E. formosa weekly, starting before whitefly is seen, once temperatures exceed 15C for a few hours each day. Use at least 1/m2/wk. Higher rates may be needed once whitefly is seen, depending on pest density and temperature. Keep susceptible plants together and monitor plants and traps weekly.
- Use Mycotal to control whiteflies if temperatures exceed 18C and RH% exceeds 80%.
- Minimise effects of pesticides on E. formosa and any leafhopper natural enemies by using biological control for other pests and IPM-compatible pesticides if necessary.
- Use lacewings, A. aphidimyza or a compatible aphicide for control of willow-carrot aphid within IPM.
Anticipated practical and financial benefits
- The annual values of UK protected pot and protected cut herbs are estimated at £17 million and £2 million respectively. With an estimated 10% susceptible plant losses due to leafhopper and 2% due to whitefly, problems with controlling both pests within IPM are causing losses to the protected herb industry of approximately £2 million p.a.
- A parasitoid of leafhopper eggs on herbs has been identified. Commercial rearing and uptake would depend on research to evaluate its efficacy and potential role within IPM. Development of a reliable biological control strategy would prevent financial losses caused by the pest and reduce the current reliance on pesticides.
- Possible reasons for unreliable control of glasshouse whitefly by E. formosa were summarised and guidelines for improved strategies given. Research on the efficacy of E. formosa on herbs and on improving the reliability of biological control of whitefly would reduce losses and improve the sustainability of IPM on protected herbs.
- The development of robust biological control strategies for leafhopper and whitefly would satisfy market demands for high quality herbs grown with minimal pesticides.
- Information collated on IPM-compatible pesticides for control of leafhoppers and whitefly on herbs will clarify the efficacy of currently available control measures.
- HDC are investigating possible Specific Off-label Approvals for use of Applaud (buprofezin) against leafhoppers on herbs and for Chess (pymetrozine) against aphids on protected lettuce, and this may be effective against both leafhoppers and whitefly on herbs. Both products are IPM-compatible but neither may be used on herbs at present. The insect-pathogenic fungus Beauveria bassiana should be available for whitefly control on all protected crops in the future.
- Strategies for control of willow-carrot aphid within IPM on herbs were identified.
SCIENCE SECTION
INTRODUCTION
Chemical control of the major pests of protected herbs is becoming increasingly difficult due to the shortage of approved pesticides, pesticide resistance and increasing demands from customers to reduce the use of pesticides. Some herb nurseries are now growing organic herbs or working towards organic production and the list of pesticides permitted for use on these crops is even more restricted. Given these pressures, biological control within an Integrated Pest Management (IPM) programme is the only sustainable strategy for pest control on protected herbs. An increasing number of specialist herb growers and those growing protected ornamentals (either pot/bedding plants or hardy nursery stock) as well as herbs are now using IPM methods.
The main pests causing problems in IPM programmes on protected herbs are leafhoppers and glasshouse whitefly. Leafhoppers are a persistent problem on many nurseries, both specialist herb nurseries and those also growing ornamentals. Although the glasshouse leafhopper, Hauptidia maroccana, can occur on herbs, the most common leafhopper is thought to be a Eupteryx species, sometimes known as the ‘sage leafhopper’. Other leafhopper species may be present on herbs, but have not been identified. The commercially available leafhopper egg parasitoid, Anagrus atomus, attacks eggs of H. maroccana but is reported not to parasitise those of Eupteryx sp. No previous research has been done on the biological control of Eupteryx sp. on herbs.
Eupteryx sp. are commonly found all year round on many herb species such as sages, rosemary, marjoram and mints, and numbers can build up rapidly, particularly during the summer, when their feeding causes severe bleaching of the foliage. The market for culinary herbs demands plants with low, or even no pest damage. Growers have relied on frequent applications of either Hostaquick (heptenophos) or nicotine to control Eupteryx sp. and this may have disrupted their IPM programmes. Hostaquick was more effective than nicotine due to its systemic activity, but this organophosphorus (OP) pesticide was revoked on 20 April 2001 as a result of the current review of anticholinesterase pesticides. An effective biological alternative for control of Eupteryx sp. is urgently needed.
Glasshouse whitefly, Trialeurodes vaporariorum is a major pest of many herb species. Biological control of this pest on herbs and other protected crops currently relies mainly on the parasitoid Encarsia formosa. However, E. formosa does not give reliable control of whitefly on a range of herb species e.g. sages, mints, marjorams and basils. Thus growers are using pesticides when whiteflies are not adequately controlled by E. formosa. The only chemical pesticides approved for control of whitefly on herbs are nicotine products and Savona, which give some control of adults, but are considered to give no or little control of the immature scale stages. Frequent applications can be necessary, which disrupt the IPM programme. A robust strategy is needed for control of glasshouse whitefly within IPM. Although extensive research has been done on glasshouse whitefly and E. formosa on tomato, no previous research has been doneon herbs.
Willow-carrot aphid, Cavariella aegopodii has recently become established on parsley on a major herb nursery. Commercially available parasitoids do not seem to attack the pest and predators were giving poor control in the Spring of 2000. Use of pesticides on the nursery would compromise the retail specifications for reduced pesticide inputs and the requirements for the organic market. The pest can also attack chervil, coriander and fennel, causing direct damage and transmitting viruses. A current LINK project (HDC project FV 228a) carried out by CSL, HRI and ADAS is developing a management strategy for parsnip yellow fleck virus on carrot, but no research has been done on control of the vector, willow-carrot aphid, on herbs.
Theobjectivesof the project are:-
1. To identify the leafhopper species occurring on protected herbs on eight representative nurseries using IPM in different parts of the country.
2. To identify any naturally-occurring leafhopper parasitoids on the same eight nurseries and to investigate their potential for commercial use.