ACTIVITY OF ENANTIOMERS OF SULCATOL ON APTERAE OF RHOPALOSIPHUM-PADI

GC-MS analysis of volatiles released from wheat infested with a high d ensity of aphids showed the presence of 6-methyl-5-hepten-2-ol (sulcat ol). The proportion of enantiomers present in the volatiles was determ ined by esterifying the mixture with (1S)-(-)-camphanic chloride and q uantifying the esters. The mixture consisted of 75% (R)-(-) and 25% (S )-(+). The mixture of enantiomers as well as the racemate showed signi ficant repellency towards apterous Rhopalosiphum padi in an olfactomet er (15.7% and 14.4%, respectively, with 10 ng of stimulus). Single ena ntiomers or a mixture containing 25% (R)-(-)- and 75% (S)-(+)-enantiom ers were inactive. The results are discussed in relation to the achiev ement of specificity by aphids in different pheromone-mediated behavio rs.