The chemical diversity of midge pheromones

Midges (Diptera: Cecidomyiidae) are pests of many economically valuable agricultural crops. The female sex pheromones of several midge species have been identified and the hypothesis was that midge sex pheromones could be chemically more diverse in structure than previously thought. This hypothesis 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, 13fi, 8Z)-2,13-diacetoxy-8-heptadecene. Four isomers were separated by high performance liquid chromatography (HPLC) and in field tests the first eluting isomer only was attractive to male midges. Addition of the second eluting isomer in 1:1 ratio greatly reduced the catches. The minor component is yet to be identified. Analysis of volatile collections from female C. pyrivora by gas chromatography (GC) coupled to electroantennographic recording (EAG) showed two consistent responses from male midges and they were identified as 2,7-diacetoxyundecane and 7-acetoxyundecane-2-one respectively. 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. Combination of the active isomer of 7-acetoxyundecane-2-one with that of 2,7-diacetoxyundecane in 1:10 ratio did not show a significant increase in the trap catch. 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. New or improved methods for rearing midges, collecting midge pheromones, setting up EAG preparation and separating stereoisomers by HPLC are reported. The pheromones identified are all novel structures; but related to those previously identified as midge sex pheromones with only one representation of the new class of components, keto acetates pheromones will provide tools for growers to monitor the pests as part of integrated pest management programmes.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Greenwich

Year dc:date.issued

2009

Author dc:creator

• Amarawardana, Lakmali

Advisors dc:contributor.advisor

• Hall, David
• Cross, Jerry

• SB Plant culture
• SF Animal culture

Language dc:language

en