Dates: April 2004 - March 2005

Funding: Defra

Countries: UK, Europe

Collaborators: Jerry Cross, East Malling Research (EMR)

NRI Project Leader: David Hall

Background

© University of Greenwich

The raspberry cane midge, Resseliella theobaldi (Barnes), is an important pest of raspberry in the UK and mainland Europe. The adult midge lays eggs in splits in young canes and larvae feed on the pith beneath the rind causing penetrating lesions, which allow entry of diseases such as the cane blight fungus, Leptosphaeria coniothyrium. The pest is controlled currently by routine sprays of the organophosphorus (OP) insecticide chlorpyrifos applied to control the first generation in spring. Recently a temperature-based forecasting model was developed for predicting spring oviposition by the raspberry cane midge to aid better timing of sprays. The forecast is believed to be accurate to ± 5 days, but still results in routine use of OP insecticides in most commercial plantations. Several other midge species have been shown to produce female sex pheromones, and development of a pheromone trap for R. theobaldi could provide a simpler and more accurate local method for monitoring midge populations.

Results
Volatiles were collected from virgin female and male midges of R. theobaldi. Four chemicals were found in volatiles from females that were not present in similar collections from the males. The major component, and probably two of the three minor components, elicited electro-antennogram responses from a male midge. These four chemicals are thus considered to be potential components of the female sex pheromone of this species.
All four female-specific chemicals have been identified and synthesized. The three minor components are 2-undecanone, 2-acetoxyundecane and 2-undecanol. The major component is a novel pheromone, 2-acetoxy-5-undecanone. It is the second example of a new class of midge pheromones, the acetoxyketones. The first example was discovered as a female sex pheromone of the apple leaf curling midge, D. mali, by the EMR/NRI team. The three chiral pheromone components have been synthesized in racemic form and the enantiomers separated by chiral HPLC. The enantiomers have also been synthesized in homochiral form to allow assignment of configuration. The compounds produced by the female midges have been shown by chiral GC to be single enantiomers with S configuration.
The S enantiomer and racemic form of the major component were shown to be highly attractive to male R. theobaldi in field tests, with loadings as low as 0.1 g being significantly attractive. Addition of the minor components did not show any consistent effect on catches. Populations of the midge were monitored at 10 sites during 2005.

© University of Greenwich

A new HortLINK project will fund future work. Growers interested in carrying out testing of the traps during 2006 are asked to complete a Registration Form (downloadable in Word (232Kb); PDF (32Kb) format).

Publications
Presentation at Soft Fruit Conference, Ashford, 23-24 November 2005, in Word (82Kb); PDF (26Kb).

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