Optimisation of the pheromone blend of the swede midge, Contarinia nasturtii, for monitoring

BACKGROUND: The swede midge, Contarinia nasturtii Kieffer, is a serious pest in crucifers. Its pheromone is a blend of (2S,9S)-diacetoxyundecane, (2S,10S)-diacetoxyundecane and (2S)-acetoxyundecane. The pheromone is used in monitoring traps, and this study examines possible ways to optimise the traps. RESULTS: Two dispenser types were compared: polyethylene dispensers and cotton dispensers. Polyethylene dispensers attracted male C. nasturtii for more than 6 weeks, whereas cotton dispensers were attractive for only 2 weeks. All three pheromone components were important for attraction of male midges in the field. The importance of the stereoisomeric compositions of the pheromone compounds was also tested - both in the wind tunnel and in the field. In the case of 2,9-diacetoxyundecane and 2-acetoxyundecane, the non-natural stereoisomers did not inhibit male C. nasturtii attraction, whereas one or both of the stereoisomers of 2,10-diacetoxyundecane did. CONCLUSION: Pheromone traps with the synthetic pheromone in a 1:2:0.02 ratio emitted from PE dispensers were highly effective and long lasting. As the mixture of stereoisomers of 2,10-diacetoxyundecane strongly inhibited attraction of male C. nasturtii while those of 2,9-diacetoxyundecane and 2-acetoxyundecane did not have any inhibitory effect, it is possible to produce traps that are effective and long lasting but cheaper to produce and maintain. (C) 2009 Society of Chemical Industry