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 erectaanalyzed by gas chromatography (GC) linked to a female Helicoverpa armigeraelectroantennograph (EAG) using polar and nonpolar capillary columns. These compounds were subsequently identified using GC linked to mass spectrometry as benzaldehyde, (S)-(–)-limonene, (R,S)-(±)-linalool, (E)-myroxide, (Z)--ocimene, phenylacetaldehyde, and (R)-(–)-piperitone. Electrophysiological activity was confirmed by EAG with a 1-g 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. erectaheadspace 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. armigerarelative to a solvent control. Similarly, a seven-component synthetic blend of EAG-active compounds identified from T. erectapresented in the same ratio (1.0 : 1.6 : 0.7 : 1.4 : 0.4 : 5.0 : 2.7, respectively) and concentration (7.2 g) 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. erectafloral volatiles.