Identification of the female sex pheromone of the pear midge, Contarinia pyrivora

Abstract: The pear midge, Contarinia pyrivora (Riley), is a pest of pear fruitlets and the damage causes severe crop losses. Although it can be controlled by application of insecticide, the timing of application is crucial as C. pyrivora is present for only a short period in the year. Identification of the female-produced sex pheromone was undertaken so that it can be used in monitoring and control of the pest. Late larvae of C. pyrivora were removed from damaged fruitlets and reared in plastic tubes individually. After sexing, volatiles were collected from both males and females by air entrainment. Collections were analysed by gas chromatography (GC) coupled to electroantennographic (EAG) recording from a male antenna, and by GC coupled to mass spectrometry (MS). Male midges showed EAG responses to two components in collections of volatiles from female. The major and the minor components were identified as 2,7-diacetoxy-undecane and 7-acetoxy-2-undecanone respectively. Stereoisomers of the synthetic pheromones were separated by HPLC on a chiral phase and the racemates, individual stereoisomers and binary mixtures were evaluated in field trapping tests. Male C. pyrivora were attracted to stereoisomer A of 2,7-diacetoxyundecane and to the first eluting stereoisomer from HPLC fractionation of 7 acetoxy-2-undecanone and these are proposed to be components of the female sex pheromone. However, results were confused by the presence of at least one other midge species in the traps and the experiments will be repeated.