HOST ATTRACTANTS FOR RED WEEVIL, RHYNCHOPHORUS-FERRUGINEUS - IDENTIFICATION, ELECTROPHYSIOLOGICAL ACTIVITY, AND LABORATORY BIOASSAY

A steam distillate from the freshly cut young bark of coconut palm Coc os nucifera was analyzed by gas chromatography, combined gas chromatog raphy-electroantennographic detection (GC-EAD) and GC-MS to detect hos t attractants for the curculionid weevil Rhynchophorus ferrugineus, on e of the major coconut pests in Sri Lanka. A twin FID peak consisting of a minor and a major component was shown to possess electrophysiolog ical (EAG) activity. The minor peak was identified as gamma-nonanoic l actone 1, while the major peak was identified as 4-hydroxy-3-methoxyst yrene 2. In an EAG assay the synthetic racemic nonanoic lactone 1 did not elicit a considerable response in the antenna of R. ferrugineus, w hereas the laboratory synthesized 2 showed activity. In a laboratory b ioassay using a Y-type olfactometer, synthetic I and 2 elicited modera te attractant properties to R. ferrugineus, whereas a 1:1 mixture of t he compounds showed increased attraction over that of the individual c ompounds.