ELECTROPHYSIOLOGICAL AND BEHAVIORAL-STUDIES OF THE BITING MIDGE, CULICOIDES IMPUNCTATUS GOETGHEBUER (DIPTERA, CERATOPOGONIDAE) - INTERACTIONS BETWEEN SOME PLANT-DERIVED REPELLENT COMPOUNDS AND A HOST-ODOR ATTRACTANT, 1-OCTEN-3-OL

Electroantennogram (EAG) and Y-tube bioassays have been used to demons trate the repellent properties of five plant compounds with host-seeki ng parous female Culicoides impunctatus Goetghebuer. The compounds wer e methyl salicylate and allyl-, butyl- phenyl- and 2-phenylethyl isoth iocyanate. EAG thresholds were 1 x 10(-3) to 1 mu g. In the bioassays, maximal repellencies occurred with 1 x 10(-2) to 10 mu g. When each c ompound was combined with 1-octen-3-ol, a confirmed host-odour attract ant for C.impunctatus females, additive effects were recorded in EAG a ssays and in bioassays, all of the compounds either reduced or reverse d the attractancy of 1-octen-3-ol. Of the isothiocyanates, allyl isoth iocyanate was the most potent and when combined with 1-octen-3-ol in f ield trials, the attractant effect of 1-octen-3-ol was reduced.