Pest Management Science (2003) 59, 538-544

Michael D. Toews and Bhadriraju Subramanyam (2003)
Contribution of contact toxicity and wheat condition to mortality of stored-product insects exposed to spinosad
Pest Management Science 59 (5), 538-544
Abstract: Spinosad, a reduced-risk commercial insecticide derived from a bacterial fermentation product, possesses both contact and oral toxicities against insects. Contact toxicity of spinosad to adults of Rhyzopertha dominica (F), Sitophilus oryzae (L), and Tribolium castaneum (Herbst) was evaluated by exposure for 24 or 48 h to treated glass Petri dishes. Adults were exposed to different deposits (0.001-0.79 mg cm^-2) of spinosad in 24-h tests and to deposits of 0, 0.0016 and 0.016 mg cm^-2 in 48-h tests. Rhyzopertha dominica was most susceptible to spinosad in 24- and 48-h tests, followed by S oryzae, and T castaneum. The 24-h LD₅₀ values were 0.0004, 0.077 and 0.189 mg cm^-2 for R dominica, S oryzae, and T castaneum, respectively. All R dominica adults were dead following 48 h exposure to both spinosad deposits, whereas mortality of S oryzae and T castaneum ranged from 10 to 85% and 12 to 48%, respectively. Rhyzopertha dominica, T castaneum, and O surinamensis adults were exposed for 14 days to whole wheat, cracked wheat and wheat flour treated with 0, 0.1 and 1.0 mg kg^-1 of spinosad. Rhyzopertha dominica adults were highly susceptible to spinosad, followed by O surinamensis and T castaneum. Immatures (eggs and larvae) of T castaneum and O surinamensis exposed for 14 days were more susceptible on spinosad-treated whole wheat than on treated cracked wheat and wheat flour. This is the first report documenting contact activity of spinosad, and the effect of grain condition on spinosad toxicity, to stored-product insects.
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Link to article at publishers website
Database assignments for author(s): Michael D. Toews, Bhadriraju Subramanyam

Research topic(s) for pests/diseases/weeds:
control - general

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tribolium castaneum
	Sitophilus oryzae
	Oryzaephilus surinamensis
	Rhyzopertha dominica