Dates: July 2003 - June 2006

Funding: Department for the Environment, Food and Rural Affairs (DEFRA)
Horticultural Development Council (HDC)
East Malling Trust

Countries: UK

Collaborators: Jerry Cross, Horticultural Research International (HRI)

NRI Project Leader: David Hall

Background

Characteristic rolling of leaves and damage to the growing point © University of Greenwich

The apple leaf midge, Dasineura mali, is a pest of apples in Europe, North America and New Zealand and in the UK it is widespread and abundant. It is particularly damaging in nurseries and newly planted orchards, causing characteristic rolling of leaves and destroying the growing point. Natural enemies are very important in regulating leaf midge numbers, especially egg parasitoids. There is currently no satisfactory method for controlling outbreaks of the pest. All apple varieties are susceptible and it is unlikely that resistant varieties can be developed. The larvae are protected inside the leaf galls they cause, and insecticides directed at emerging and ovipositing adults can devastate natural enemies. Previous work has demonstrated that virgin female apple leaf midges produce a pheromone that attracts the males, and also that mated females are attracted to volatiles from apple foliage.

Results

Apple leaf midge © University of Greenwich

This project will aim to identify and synthesise the components of the pheromone and develop traps for monitoring the pest. If time permits, similar work will be done to identify attractive components of volatiles from apple foliage and evaluate their use in trapping systems. The traps will then be used to follow up previous work by HRI on critical timing of application of selective insecticides against the adult midges to optimise kill of the pest and minimise the effect on natural enemies.
To date volatiles have been collected from large numbers of virgin female midges. These are active in a laboratory bioassay and show a single, highly active response in linked GC-EAG analyses. Although amounts of material are tiny, EI and CI mass spectra have been recorded and identification is in progress.

Uptake

Outputs of the project will be disseminated to growers as part of the project.

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