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 of 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 probability-based computer mass spectral library search indicated the best matches for the compounds in the most EAG-active fractions to the tridecan-2-one, (E,E)-3,5-octadien-2-one, (E,Z)-2,6-nonadienal, and (E)-2-nonenal. EAG, mass spectral, and retention time data of the synthetic compounds were consistent with compounds in the purified EAG-active fractions. 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 indicate 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.