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Title: Sex ratio in Diabroticina beetles (Coleoptera: Chrysomelidae) on cucurbitacin traps and baits depends on the distribution of the attractant source

Author
item CABRERA WALSH, GUILLERMO - USDA/ARS/SABCL
item WEBER, DONALD - USDA/ARS
item MATTIOLI, FEDERICO - UNIV. OF BUENOS AIRES

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2007
Publication Date: 3/27/2008
Citation: Cabrera Walsh, G., Weber, D.C., Mattioli, F. 2008. Sex ratio in Diabroticina beetles (Coleoptera: Chrysomelidae) on cucurbitacin traps and baits depends on the distribution of the attractant source. Journal of Applied Entomology.Pages 205-215

Interpretive Summary: Cucurbit juices rich in cucurbitacins attract large numbers of leaf beetles, for which they have been applied in traps and toxic baits. However, field trials reveal that males are far more attracted than females, which could mean that females are still capable of laying enough eggs for the larvae to cause heavy damage in the roots of maize and other crops. In this work we assessed the sex ratio of corn rootworms on cucurbitacin baited sticky traps, and of the beetles killed by application of cucurbitacin based toxic baits at two different scales: a small area of 100 m2, and a larger area of 10,000 m2. Traps and small area bait applications attracted mostly males, but the 1-ha treated plot showed a much less biased sex ratio. The male bias in sex ratio depends on the areal extent of the cucurbitacin source. We conclude that the attraction range of a point source of cucurbitacin is quite short, and almost limited to males, whereas a toxic bait applied over a large area should provide a good control of both sexes within the treated area. No significant non-target effects were observed for any of the tests.

Technical Abstract: Cucurbitacin-rich juices attract large numbers of diabroticine beetles of many species, for which they have been studied and applied in traps and toxic baits. Although laboratory tests indicate both males and females feed avidly on them, field trials reveal that males are far more attracted than females. In this work we assessed the sex ratio and attraction range of beetles trapped on cucurbitacin baited, wind oriented, sticky traps, and of the beetles killed by application of cucurbitacin based toxic baits at two different scales: a small area of 100 m2, and a larger area of 10,000 m2. Also, non-target effects were assessed for every test. The attraction range of marked Diabrotica speciosa to cucurbitacin-containing sticky traps was 10 to 20 m. Traps and small area bait applications attracted mostly males (99.85% on the traps; 95.2% with the bait), but the 1-ha treated plot showed a much less biased sex ratio (57% male). The male bias in sex ratio depends on the areal extent of the cucurbitacin source. We conclude that the attraction range of a point source of cucurbitacin is quite short, and almost limited to males, whereas a toxic bait applied over a large area should provide a good control of both sexes within the treated area. No significant non-target effects were observed for any of the tests.