ELECTROANTENNOGRAM-ACTIVE COMPONENTS OF MAIZE SILK FOR ADULTS OF THE WESTERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

Volatile silk semiochemicals of maize, Zea mays L., are attractive to adults of Diabrotica virgifera virgifera LeConte. Senescing portions o f silks (the brown portion that protrudes from the tip of the ear) are highly electroantennogram (EAG) active, and solvent extracts of these portions of silks were evaluated in a sequential fractionation scheme to isolate and identify the primary EAG-active components. A probabil ity-based computer mass spectral library search indicated the best mat ches for the compounds in the most EAG-active fractions to the trideca n-2-one, (E,E)-3,5-octadien-2-one, (E,Z)-2,6-nonadienal, and (E)-2-non enal. EAG, mass spectral, and retention time data of the synthetic com pounds were consistent with compounds in the purified EAG-active fract ions. The data show strong EAC-responses to tridecan-2-one, (E,E)-3,5- octadien-2-one, (E,Z)-2,6-nonadienal, and (E)-2-nonenal but does not i ndicate the type of behavioral response (if any) associated with these compounds. EAG tests with related compounds are discussed in terms of structure-EAG activity relationships.