| Summary: | The hypothesis that midge sex pheromones could be chemically more diverse in structure than previously thought was tested in the context of four midge species of importance to UK horticulture: pear leaf midge, Dasineura pyri; pear midge, Contarinia pyrivora; blackcurrant midge, D. tetensi; and blackberry midge, D. plicatrix. The major component of the pheromone of D. pyri was identified as (2R, 13R, 8Z)-2, 13-diacetoxy-8-heptadecene. Four isomers were separated by HPLC and in field tests the first eluting isomer only was attractive to male midges. Analysis of volatile collections from female C. pyrivora showed two consistent responses from male midges and they were identified as 2,7-diacetoxyundecane and 7-acetoxyundecane-2-one. The field testing with isomers of 2,7-diacetoxyundecane separated by HPLC revealed that the first and the third eluting isomers were attractive. The racemic 7-acetoxyundecane-2-one was active as well as the first eluting isomer from HPLC. Two EAG active components were detected in D. tetensi female volatile collections. The major component was identified as (Z)-2,12-diacetoxy-8-heptadecene and after separation of stereoisomers by HPLC the third eluting isomer has shown to be attractive to male D. tetensi in the field. The structure for the minor component was proposed as a keto-acetate homologue of the corresponding major component. Preliminary work carried out on identification of the female sex pheromone of D. plicatrix indicated two responses from conspecific males. These were shown to be 15-carbon acetates with the acetate function at C-2, probably with two and one double bonds respectively.
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