Submitted to: Journal of Asia-Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2010
Publication Date: 1/15/2011
Publication URL: http://handle.nal.usda.gov/10113/55891
Citation: Kamalalkannan, S., Murugan, K., Barnard, D.R. 2011. Toxicity of Acalypha indica (Euphorbiaceae) and Achyranthes aspera (Amaranthaceae) leaf extracts to Aedes aegypti (Diptera: Culicidae). Journal of Asia-Pacific Entomology. 14:41-45. Interpretive Summary: The main threat to effective control of disease-transmitting mosquitoes is resistance to synthetic insecticides in the mosquito vector population. Botanical insecticides may be a suitable alternative to the use of synthetic insecticides for vector control. They are relatively safe, biodegradable, and can usually be obtained from local sources. In this study, Bharathiar University (India) and ARS scientists evaluated phytochemicals from two plants that occur in India (a type of spurge and a type of amaranth) for toxicity to the larvae and adults of the Yellow Fever mosquito (Aedes aegypti). The phytochemicals caused significant mortality in mosquito larvae and when burned in mosquito coils, reduced fecundity of females and egg fertility. The results of the study suggest that phytochemicals from spurge and amaranth plant species may provide effective control of immature and adult mosquitoes.
Technical Abstract: 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.