Ylva HlLLBUR, Jan LÖFQVIST
Swedish University of Agricultural Sciences, Dept. of Plant Protection,
Div. of Chemical Ecology, P. O. Box 44, S-230 53 Alnarp, Sweden
The pea midge, Contarinia pisi, is a sporadic and localised pest of vining peas throughout northern Europe. Emergence and migration of adults to pea fields is often sudden. This presents a problem for control, because insecticides are effective only against the adults before oviposition. Therefore a local and accurate monitoring system is much needed (1). The aim of our work is to develop a well functioning monitoring system, based on pheromone traps, that allows precise predictions about pea midge emergence. The first step is to identify the sex pheromone of the female pea midges.
ln the field, female pea midges attract males from a distance by emitting sex pheromones (2). We have confirmed this in the laboratory, where windtunnel tests have been carried out with both caged, calling females, and female extract as bait. Of the tested males (n=57), 58% flew up to the female cage and made attempts to copulate. The male flight in the windtunnel, consisting of zigzagging and straight upwind flight, resembles the flight behaviour described for male moths.
Furthermore, we have developed a method for collection on glass of the substances emitted by the females. Collections have been made from both males and females. Differential analyses of gas chromatograms of female and male effluvial extracts respectively, show that the female extract contains two components that are absent in the male extract. Chemical identification of these is now going on.
EAG (electroantennogram) recordings were performed on male antennae. In these, the response to pipettes that had contained calling females, was compared to the response to blank pipettes. The female pipettes elicited significantly higher responses than did the blank (T=-2,899, d.f.=48, p=0,006). So far though, certain methodological problems due to the small size (2 mm) and fragility of the pea midges, have prevented us from proceeding with further electrophysiological studies such as GC-EAD and single cell recordings.
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