The naturally derived insecticide spinosad is highly toxic to Aedes and Anopheles mosquito larvae.
Spinosad is a naturally derived biorational insecticide with an environmentally favourable toxicity profile, so we investigated its potency against mosquito larvae (Diptera: Culicidae). By laboratory bioassays of a suspension concentrate formulation of spinosad (Tracer), the 24 h lethal concentration (LC50) against Aedes aegypti (L.) third and fourth instars was estimated at 0.025 p.p.m. following logit regression. The concentration-mortality response of third- and fourth-instar Anopheles albimanus Weidemann did not conform to a logit model. The LC50 value of spinosad in Anopheles albimanus was 0.024 p.p.m. by quadratic linear regression. A field trial in southern Mexico demonstrated that spinosad 1 p.p.m. compared with the standard temephos (Abate) 1% granules 100 g/m3 water prevented Ae. aegypti breeding in plastic containers of water for 8 weeks; at 10 p.p.m. spinosad prevented breeding for > 22 weeks. In another field trial, spinosad at 5 p.p.m. and temephos both completely eliminated reproduction of Ae. aegypti for 13 weeks. In contrast, the bacterial insecticide Bacillus thuringiensis var. israelensis (Bti, Vectobac) AS) performed poorly with just 2 weeks of complete inhibition of Ae. aegypti breeding. Spinosad also effectively prevented breeding of Culex mosquitoes and chironomids in both trials to a degree similar to that of temephos. We conclude that spinosad merits evaluation as a replacement for organophosphate or Bti treatment of domestic water tanks in Mesoamerica. We also predict that spinosad is likely to be an effective larvicide for treatment of mosquito breeding sites.
ECOSUR, Tapachula, Chiapas, Mexico.
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Bond
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Marina
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Williams
D000330:Aedes; D000818:Animals; D000852:Anopheles; D001413:Bacillus thuringiensis; D004338:Drug Combinations; D007300:Insect Control / Q000379:methods*; D007306:Insecticides; D016014:Linear Models; D018942:Macrolides; D008800:Mexico; D000002:Temefos
D004338:Drug Combinations; D007306:Insecticides; D018942:Macrolides; D000002:Temefos; C415329:spinosad