Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2007
Publication Date: 3/13/2008
Citation: Walsh, G.C., Weber, D.C., Mattioli, F., Heck, G. 2008. Qualitative and quantitative responses of Diabroticina (Coleoptera: Chrysomelidae) to cucurbit extracts linked to species, sex, weather and deployment method. Journal of Applied Entomology. Vol. 132(3):205-215.
Interpretive Summary: Field and laboratory experiments were designed to evaluate the power of traps based on leaf beetle attractants called cucurbitacins. These traps attracted a great number of leaf beetles of many species. However, only males responded to the extracts deployed. The weather factors influencing catches were evaluated, and no single factor resulted responsible for the yield of the traps. However, barometric pressure and temperature combined in complex ways as predictors. The surrounding beetle density on its own did not predict the trap yields either. Finally, several species of wild cucurbits were evaluated to determine the best candidate for commercial production, and a wild species, Cucumis myriocarpus and a mutant bitter watermelon were determined to be the best candidates. Although the susceptibility to weather conditions and a strong male dominance in the catches raise the question of the usefulness of cucurbitacins as the main component in toxic baits or traps, these drawbacks may prove to be less important in widespread bait applications and Diabroticina management in vegetable crops.
Technical Abstract: Toxic baits and traps for Diabroticina, based on bitter cucurbit extracts, have been utilized for a number of years with inconsistent results. Four species of bitter Cucurbitaceae were compared in the field for their attractancy to species of Diabroticina in Argentina and the U.S. The comparisons were made with polyester fabrics treated with known volumes of different cucurbit extracts, against a standard cucurbit extract of bitter Hawkesbury watermelon (Citrullus lanatus (Thunberg) Matsumura & Nakai). The factors evaluated were: the attractancy of the different extracts in terms of beetle numbers, species and sex of the Diabroticina caught; influence of different fabrics on such attraction; and influence of several weather variables on the catches. The most attractive specie was Cayaponia bonariensis (Miller) Martinez Crovetto, however, practical considerations indicated that Cucumis myriocarpus Naudin and Hawkesbury watermelon may be better choices from the commercial perspective. No single weather factor could explain the catches throughout the sample range, but different temperature and barometric pressure ranges provided some predictive value. Although the susceptibility to weather conditions and a strong male dominance in the catches raise the question of the usefulness of cucurbitacins as the main component in toxic baits or traps, these drawbacks may prove to be less important in widespread bait applications and Diabroticina management in vegetable crops.