Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/1996
Publication Date: N/A
Interpretive Summary: Corn rootworm adults are attracted to the blossoms of squash plants, and feed compulsively on squash tissues (especially the more bitter varieties). The compounds responsible for the attraction to squash blossoms and the compulsive feeding have been previously identified. Corn rootworm adults are also attracted to corn silk, but the volatile compounds responsible for this attraction have not been identified. Volatiles from corn silk were evaluated using an electroantennogram (EAG) technique (the EAG measures the responses of neurons in the antennae of an insect to volatile compounds and compounds that are EAG-active or commonly behaviorally active). Senescing portions of silks (the brown portion that protrudes from the tip of the ear) are the most EAG active, and solvent extracts of these portions of silks were evaluated in a sequential fractionation scheme in order to isolate and identify the primary EAG-active components. The compounds in the most EAG-active fractions were tridecan-2-one, (E,E)-3,5-octadien-2-one, (E,Z)-2,6- nonadienal, and (E)-2-nonenal. The identifications were verified by comparing synthetic versions of the identified silk compounds using EAG activity, mass spectra, and retention-time data. The data from the synthetic compounds were consistent with the compounds identified from the purified EAG-active fractions.
Technical Abstract: The chemical ecology of corn rootworm adults has been extensively investigated in terms of their interactions with plants in the genus Cucurbita, but not their major host, corn (Zea mays L.). Volatile corn silk compounds are attractive to Diabrotical virgifera virgifera LeConte (western corn rootworm) adults. Senescing portions of silks (the brown portion that protrudes from the tip of the ear) are the most electroantennogram (EAG) active, and solvent extracts of these portions of silks were evaluated in a sequential fractionation scheme in order 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 be tridecan-2-one, (E,E)-3,5-octadien-2-one, (E,Z)-2,6-nonadienal, and (E)-2-nonenal. Mass spectra, EAG, and retention-time data of the synthetic compounds were consistent with compounds in the purified EAG-active fractions. Tests with related compounds are discussed in terms of structure/EAG activity relationships.