Factsheet Factsheet Factsheet 05/01 Horticultural Bradbourne House Development East Malling Herbs Council Kent ME19 6DZ T: 01732 848383 F: 01732 848498 Project No. PC 178 E: [email protected]
Glasshouse whitefly and leafhoppers in protected herbs: options for control within IPM programmes
by Jude Bennison, ADAS Boxworth
Options for the control of glasshouse whitefly and leafhoppers in protected herbs within IPM programmes were evaluated in a recent survey and literature search. This factsheet describes the main leafhopper species damaging protected herbs, identifies a potential new leafhopper egg parasitoid and provides guidance on the control of whitefly with the parasitoid Encarsia formosa. The efficacy of currently available IPM-compatible pesticides against both whiteflies and leafhoppers on protected herbs is discussed.
Background leafhoppers and glasshouse whitefly essential due to the low or ‘zero’ can be a problem. At a conservative tolerance for pests or damage on The annual value of the UK protected estimate of 10% susceptible plant culinary herbs. Robust strategies for pot and cut herb industry is estimated losses due to leafhopper and 2% due the control of leafhopper and whitefly at £17 million and £2 million, to whitefly, difficulties in controlling within IPM need to be developed and respectively. Whilst protected herb both pests are causing losses to the this factsheet aims to outline currently growers have successfully adopted protected herb industry of available control options. IPM techniques as a means of approximately £2 million annually. sustainable pest control, control of Effective control of all pests is
Adult chrysanthemum leafhopper or ‘sage leafhopper’, Eupteryx melissae Eupteryx melissae nymph Leafhopper The main leafhopper species damaging protected herbs has been confirmed as Eupteryx melissae, the chrysanthemum leafhopper, often known by growers as the ‘sage leafhopper’. Adult E. melissae are approximately 3 mm long, pale green with distinctive brown and black markings on the body and wings. They are very active and hop from the plants when disturbed. The eggs are laid in the leaf veins and petioles and are not easily detected even under a microscope. The young nymphs are pale yellowish green and the older nymphs develop dark brown bands across the body and tips of the wing buds. The nymphs are much less mobile than the adults and are usually Cast skins of Eupteryx melissae nymphs © Holt Studios found under the leaves next to a leaf vein. There are five nymphal stages and when each stage moults, the cast skins are left behind on the leaf, which can be mistaken for live leafhoppers.
Leafhopper damage Plant losses due to leafhopper can range from 1 to 50 % with significant Sages are the main herb species additional costs incurred in time spent damaged by E. melissae but balm, spraying, picking off damaged leaves basil, bergamot, French lavender, prior to sale and selecting plants for mints, marjorams, oregano, rosemary cutting. In a survey of commercial and thymes can also be affected. nurseries, the pest was present all year Leafhopper damage appears as white round but damage was most severe or pale yellow spots on the leaves during the late spring to early autumn which later coalesce to form bleached period. areas leading to necrosis. On badly damaged leaves, small black faecal spots are also visible. Leafhopper damage to thyme
Leafhopper damage to sage © Holt Studios Leafhopper damage to marjoram Leafhopper damage to rosemary veins or petioles. The A. atomus larva Leafhopper and pupa develops inside the parasitoid leafhopper egg. Parasitised eggs turn a dark brown colour and with In a survey of commercial nurseries, experience, some can be recognised naturally occurring leafhopper egg with a hand lens. When the adult A. parasitoids were found on herbs atomus is fully developed, it cuts a collected from half the nurseries round hole in the egg and emerges visited. The highest numbers of this onto the leaf. parasitoid were found on organically- A. atomus is commercially available grown rosemary which had not been for the control of the glasshouse treated with pesticides. The leafhopper on crops such as tomato, parasitoids were confirmed as but this parasitoid has been reported belonging to the Anagrus atomus not to attack E. melissae. The A. species group. Adult A. atomus are atomus strain found in this project is tiny parasitic wasps, less than one mm likely to be adapted to E. melissae and long. The wings are fringed with long may have potential for commercial hairs. Female wasps lay their eggs rearing and use within IPM inside the leafhopper eggs in the leaf programmes. Adult Anagrus atomus © Holt Studios
No research has been done on the herbs means that no firm guidelines Glasshouse whitefly factors affecting the success of E. can be provided to herb growers on Difficulties in controlling glasshouse formosa against glasshouse whitefly the use of Encarsia to control whitefly. whitefly on herbs with the parasitoid on herbs. However, the success of Recommendations are based on the Encarsia formosa were reported during Encarsia on other crops is known to be use of Encarsia in ornamental crops the survey of commercial nurseries. affected by whitefly density and where there may be similarities in the The pest was a severe problem on potential sources of infestation, production systems, but there is no sages, lemon verbena, mints, parasitoid introduction rate and guarantee that using the guidelines marjorams, bergamot, basil, balms and timing, temperatures, crop species, given below will lead to effective rue. Infested stock plants were production methods and pesticides whitefly control on herbs. thought to be a frequent source of the used. The lack of supporting data for pest.
minimum of 1/m2/week before small or hairy leaves such as sage. Guidelines for whitefly is seen and from when Problem plants may need to be temperatures exceed 15°C. Once grouped and whitefly controlled optimising whitefly whitefly is seen, higher Encarsia with IPM-compatible pesticides. introduction rates are likely to be control by Encarsia needed and these will depend on • Pesticides: There are some IPM- formosa pest density, temperature and crop compatible pesticides available for species. whitefly control on herbs and • Introduction strategy: Introduce details are listed in the table. Encarsia weekly as soon as • Herb production time: Pot herb Pesticide applications may be temperatures are suitable, rather crops are produced in only 5-6 necessary to reduce early season than waiting until the ‘first’ whitefly weeks in the summer. Due to whitefly on stock or production is seen. Even at optimal whitefly development rate there plants when temperatures are too temperatures, if releases start too may be insufficient time for adult low for Encarsia, or to control late, Encarsia never catches up Encarsia to emerge from whitefly ‘hotspots’. The IPM- with the whitefly and control fails. parasitised scales, or even for compatible pesticides listed in the parasitised scales to turn black table are either safe to Encarsia or • Temperatures: Encarsia can walk or before marketing. Thus Encarsia harmful for up to only four days. fly at 15°C but are more active at host-feeding is likely to be more However,even pesticides with 18°C. On sunny winter days, important than parasitism for short persistence can interrupt temperatures can exceed 15°C in whitefly control on herbs. To biological control if used too unheated glasshouses and maintain adequate host-feeding, frequently. tunnels. Start introducing Encarsia Encarsia need to be introduced as soon as temperatures exceed every week. • Cultural practices: To help 15°C for a few hours each day. minimise whitefly infestations, • Herb plant characteristics: Control weeds should be controlled in and • Introduction rate: Specific with Encarsia may not be reliable around glasshouses/tunnels. introduction rates for herb crops on all herb species. Plants Infested stock plants can often be have not been established. producing strongly scented a source of early season whitefly However,as a general rule, if too volatiles may be repellent to infestations and should be kept in few Encarsia are released, control Encarsia. Encarsia searching for a separate structure to production will fail. Therefore aim for ‘overkill’ whitefly scales are likely to be plants and kept as free from by introducing Encarsia at a slowed down on plants with many whitefly infestation as possible. Control of leafhopper species occurring on herbs Approved IPM-compatible pesticides and use of the most effective for both leafhopper and whitefly leafhopper and pesticide, Hostaquick (heptenophos) control are listed in the table. whitefly with is no longer permitted as approval was revoked on 20 April 2001. pesticides Control of glasshouse whitefly on herbs with the parasitoid E. formosa There is currently no biological control can be unreliable but guidelines have agent available for the main been provided to optimise control.
repeated sprays are needed and • Dichlorvos may give some control Efficacy of currently Savona may only be used once per of whitefly adults and leafhoppers crop on herbs. but safety to herb crops should available pesticides first be tested. Dichlorvos is against leafhopper • Nicotine products give limited currently being reviewed under the control of whitefly adults and anticholinesterase pesticides and whitefly should give some control of review. The outcome of this review leafhoppers. However, repeated will be available shortly. • Mycotal controls whitefly if applications are necessary which temperatures and relative can disrupt IPM. • Cypermethrin products may give humidities are high enough (18°C partial control of leafhopper but and 80% RH respectively). Such • Eradicoat should control whitefly are unlikely to control whitefly. conditions are only likely to occur pupae and give some control of Cypermethrin products are harmful regularly in herb propagation younger scale stages. It has not to biological control agents for up houses. Mycotal has not been been tested against leafhoppers. to 3 months after application and tested against leafhopper. in IPM should only be used as a • Spraying Oil may give some clean-up treatment on stock plants • Savona should control whitefly control of whitefly but neither at the end of the season or on adults and scale stages and give leafhopper control nor safety to plants just before sale. partial control of leafhoppers, but herbs has been tested.
Where next? • HDC are investigating the potential • Since many of the IPM-compatible for SOLA’s for Chess (pymetrozine) pesticides have contact action, • A potential strain of the parasitoid, for the control of whitefly and methods of pesticide application Anagrus atomus has been leafhopper on protected herbs, and to herbs need to be developed to identified for the control of for Applaud (buprofezin) for the improve in particular, coverage of leafhopper on herbs. Further control of leafhopper. The insect- the undersides of the leaves. research is needed to assess its pathogenic fungus Beauveria commercial potential. bassiana may be approved for control of whitefly on protected • Reliable control of whitefly with crops later this year. None of these Encarsia formosa may not be products are currently approved achievable on herbs and alternative for use on protected herbs. biological control agents may need to be sought.
Further information may be obtained from the HDC Whilst reports issued under the auspices of the HDC © 2001 Horticultural Development Council. No part Project Report available from the Office. are prepared from the best available information, of this publication may be reproduced in any form or neither the authors or the HDC can accept any by any means without prior permission of the responsibility for inaccuracy or liability for loss, Horticultural Development Council. damage or injury from the application of any concept or procedure discussed. HDC Factsheet 05/01 Glasshouse whitefly and leafhoppers in protected herbs: options for control within IPM programmes
Table 1. IPM compatible pesticides approved for use on protected herbs with some efficacy against whitefly and leafhopper (October 2001)
Active Trade Approval Application Rec. for Rec. for Persistence ingredient name status conditions whitefly leafhopper against control control Encarsia
Dichlorvos Luxan SOLA 0625/99 Use as a high * * 3-4 days Dichlorvos for use on volume spray 600# protected lettuce1
SOLA 0626/99 Use as a * * for use on thermal fog protected herbs1
Fatty acids Savona On-label Max. one Yes * 0 days approval for application use on per herb crop lettuce1,3
Natural Majestik Not subject to Avoid treating Yes Yes 24 hours organic plant pesticide close to extract regulations 2 harvest as may leave a sticky deposit
Plant and Eradicoat Not subject to Apply to oil- Yes * 0 days vegetable oil pesticide tolerant plants extracts regulations 2 only
Nicotine Nicotine On-label 16°C or above Yes Some 3-4 days 40% approval for needed during reduction Shreds protected application herbs
Nico Soap On-label * * approval for use on lettuce1
No-Fid * *
XL-All Yes (partial Yes Insecticide / control XL-All only) Nicotine 95%
Petroleum oil Hortichem Not subject to Apply to oil- * * 0 days Spraying Oil pesticide tolerant plants regulations 2 only
Verticillium Mycotal On-label Needs Yes * 0 days lecanii approval for minimum use on 18°C and 80% protected RH lettuce1,3
HDC Factsheet 05/01 Glasshouse whitefly and leafhoppers in protected herbs: options for control within IPM programmes
1 Can be used off-label at own risk under the Revised Long Term Arrangements for Extension of Use (2000). Pesticides approved or with Specific Off Label Approval (SOLA) for use on ‘protected lettuce’ or ‘lettuce’ (but not if label specifies only ‘outdoor lettuce’) may be used on protected herbs, provided that all label or SOLA conditions relating to use on lettuce are observed. 2 Acts by physical means only, so is not subject to the pesticide regulations. Use on any crop and number of applications is at grower’s own risk. 3 Permitted by the Soil Association for use on organic crops. * No label recommendation for this particular pest, but may have some efficacy. # Dichlorvos is currently being reviewed under the anticholinesterase pesticides review. The outcome of this review will be available shortly.
Note Regular changes occur in the approved status of pesticides arising from changes in the pesticide legislation or for other reasons. For the most up to date information, please check with professional supplier or with the Information Office at the Pesticides Safety Directorate (PSD) Tel: 01904 640500.
· Always read the label or the Specific Off-label (SOLA) notice of approval as appropriate. · Use pesticides safely. · Check with suppliers for full details of any side effects on biological control agents.
Whilst factsheets issued under the auspices of the HDC are prepared © 2001 Horticultural Development Council. from the best information, neither the authors or the HDC can accept No part of this publication may be reproduced in any form or by any any responsibility for inaccuracy or liability for loss, damage or injury means without prior permission of the Horticultural Development from the application of any concept or procedure discussed. Council.