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Toxicity of Acalypha indica (Euphorbiaceae) and Achyranthes aspera (Amaranthaceae) leaf extracts to Aedes aegypti (Diptera:Culicidae)

Kamalakannan, Siva, Murugan, Kadarkarai, Barnard, Donald R.
ARS USDA Submissions 2011 v.14 no.1 pp. 41
Acalypha indica, Achyranthes aspera, Aedes aegypti, blood, botanical insecticides, chickens, females, hematophagy, insecticidal properties, larvicides, leaf extracts, lethal concentration 50, methanol, pupae, smoke, toxicity
Alternative control technologies envisioned for the dengue vector Aedes aegypti L. (Diptera: Culicidae) include botanical insecticides, which are believed to pose little threat to the environment or to human health and may provide a practical substitute for synthetic insecticides. In this study, we determined the biological activity of methanol extracts of the leaves of Acalypha indica L. (Euphorbiaceae) and Achyranthes aspera L (Amaranthaceae) and of the combined extract (A. indica + A. aspera) as a botanical insecticide against Ae. aegypti. The median lethal concentrations (LC50) for 4th instar Ae. aegypti were 277 ppm (combined extract), 409 ppm (A. aspera) and 420 ppm (A. indica). Respective LC50 values for pupae were 326 ppm, 456 ppm, and 467 ppm. In studies of smoke toxicity, 64% of females exposed to negative control smoke (no extract) blood fed on chicken, whereas 17% blood fed when exposed to smoke from coils containing A. aspera extract and smoke from the positive control (0.2% d-allethrin). In the field, there was a significant relationship between the treatment of water storage tanks with plant extract and change in larval and pupal populations, which decreased in the tank receiving the combined extract by 97% and 81%, respectively, after 5 days. Given the results of this study, further evaluation of the combined (A. indica + A. aspera) extract as a mosquito larvicide is warranted. Mosquito coils with A. aspera extract also show promise as a practical and potentially economical means for mitigating mosquito blood feeding