Electrophysiological and behavioral responses of female Helicoverpa armigera to compounds identified in flowers of African marigold, Tagetes erecta

Seven electrophysiologically active compounds were detected in air-entrained headspace samples of live flowers of Tagetes erecta analyzed by gas chromatography (GC) linked to a female Helicoverpa armigera electroantennograph (EAG) using polar and nonpolar capillary columns. These compounds were subsequently identified using GC linked to mass spectrometry as benzaldehyde, (S)-(-)-limonene, (RS)-(+/-)-linalool, (E)-myroxide, (Z)-beta -ocimene, phenylacetaldehyde, and (R)-(-)-piperitone. Electrophysiological activity was confirmed by EAG with a 1-mug dose of each compound on filter paper eliciting EAG responses that were significantly greater than the solvent control response from female moths. Wind-tunnel bioassays with T erecta headspace samples, equivalent to 0.4 flower/hr emission from a live flower, elicited a Significant increase in the number of upwind approaches from female H. armigera relative to a solvent control. Similarly, a seven-component synthetic blend of EAG-active compounds identified from T. erecta presented in the same ratio (1.0: 1.6: 0.7: 1.4: 0.4: 5.0: 2.7, respectively) and concentration (7.2 mug) as found in the natural sample elicited a significant increase in the number of upwind approaches relative to a solvent control during a 12-min bioassay that was equivalent to that elicited by the natural T erecta floral volatiles.