Role of plant odor in parasitism of European corn borer by braconid specialist parasitoidMacrocentrus grandii Goidanich: Isolation and characterization of plant synomones eliciting parasitoid flight response.

In an earlier study we documented attraction of the specialist parasitoidMacrocentrus grandii Goidanich to odors of com, potato, and snap bean. In the present study the chemical bases of the parasitoid's attraction to these food plants of its European corn borer host were compared. Volatile compounds from corn leaves were isolated using Tenax and identified by capillary gas chromatographic-mass spectrometry. Twenty-one compounds including aldehydes, ketones, alcohols, esters, and sesquiterpenes were present in corn. These were separated into fractions by column chromatography on Florisil. Wind-tunnel bioassays of the fractions indicated thatM. grandii was attracted to fractions containing nonpolar and slightly polar compounds including sesquiterpenes, aldehydes, a ketone, and esters. More polar compounds in corn, like alcohols, were not attractive. Attraction to potato odor was based on the presence of the same classes of compounds that were attractive in corn, but more polar compounds were involved in attraction to snap bean odor. This study indicated that only some compounds in each of the three odor complexes tested were attractive. It also documented that different compounds were involved in attraction ofM. grandii to different plant odors.