Electrophysiological responses of female Helicoverpa armigera (Hubner) (Lepidoptera; Noctuidae) to synthetic host odours

Studies were conducted to investigate the electroantennographic (EAG) respo nses of adult female Helicoverpa armigera to a range of known and putative kairomone components. The studies show that at a given dose the EAG respons es elicited by a series of straight-chain aliphatic primary alcohols were n ot dependent on volatility since butan-1-ol and pentan-1-ol elicited EAG re sponses that were significantly smaller than those elicited by hexan-1-ol. The amplitudes of responses to hexan-1-ol were found to be dose dependent w ith a dose of 10(-1) mu mol at source in a non-volatile solvent eliciting t he largest response. Similarly, changes in functionality in a range of C-6 straight-chain aliphatic compounds significantly changed the amplitude of r esponse elicited, with aldehydes eliciting smaller responses than the relat ed primary alcohols and saturated compounds eliciting higher responses than related unsaturated compounds. Of the range of nine host plant-produced te rpenoids tested, ocimene and beta -phellandrene elicited the highest respon ses and of the six aromatic compounds tested phenylacetaldehyde and benzald ehyde elicited the largest responses, at the doses tested. The significance of these findings for analysis of floral odours by gas chromatography link ed to electroantennography as a means of identifying kairomone components a ttractive to H. armigera are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.