Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/1997
Publication Date: N/A
Interpretive Summary: Buffalo gourd root powder contains potent, nonvolatile feeding stimulants for western corn rootworm adults, and baits containing this powder mixed with insecticide have become a viable alternative to granular soil insecticides. Field observations of these baits have indicated that volatile attractants may also be present. Electroantennogram (EAG) recording is usually helpful in detecting the most important behaviorally-active components in a volatile blend (the EAG measures the responses of neurons in the antennae of an insect to volatile compounds). Solvent extracts of buffalo gourd root powder were evaluated for EAG activity to western corn rootworm adults and the primary EAG-active components were isolated and identified (short chain aldehydes, ketones, and alcohols). The identifications were verified by comparing synthetic versions of the identified compounds to the natural compounds using mass spectra, retention time, and EAG data. The data from the synthetic compounds were consistent with the natural compounds. Several compounds identified in the current study were previously identified from the most EAG-active fractions from maize silk extracts. The current study contributes basic knowledge on how corn rootworms may have switched from their ancestral host (squash) to their current host (corn). Compounds identified could also be useful in sampling adults of this major pest.
Technical Abstract: Buffalo gourd, Cucurbita foetidissima Kunth, root powder contains potent nonvolatile feeding stimulants for Diabrotica virgifera virgifera LeConte (western corn rootworm) adults, and baits containing this powder mixed with insecticide have become a viable alternative to granular insecticide. Anecdotal evidence has indicated that these baits may also contain volatile eattractants. Solvent extracts of buffalo gourd root powder were evaluated for electroantennogram (EAG) activity to western corn rootworm adults, and a sequential fractionation scheme was conducted to isolate and identify the primary EAG-active components in the extract. A probability-based computer mass spectral library search indicated that the best matches for compounds in the most EAG-active fractions to be (E,E)-3,5-octadien-2-one, (E,Z)-2,6-nonadienal, (E)-2-nonenal, phenyl alcohol, benzyl alcohol, (E,E)-2,4-decadienal, and 6,10-dimethyl-5,9-undecadien-2-one. Retention time, mass spectral, and EAG data of the synthetic compounds were consistent with compounds in the purified EAG-active fractions (synthetic material was unavailable for 6,10-dimethyl-5,9-undecadien-2-one). Previous work indicated that several of these same compounds were in the most EAG-active fractions from maize silk. EAG data are discussed in terms of possible evolutionary considerations.