Vol. 8, Issue 6, Part A (2021)

Author(s): Anjali Rawani, Anupam Ghosh and Goutam Chandra

Abstract: Plant-based insecticides are eco-friendly, target-specific, less harmful to non-targets, biodegradable, and less prone to developing resistance. The present study was carried out to evaluate the mosquito larvicidal activity of crude and ethyl acetate solvent extracts of the stem, root, and flower of Solanum nigrum L. against immatures of Culex quinquefasciatus Say. Early third instar larvae of Cx. quinquefasciatus were exposed to 1, 1.5, 2, 2.5 and 3% of crude and 30, 50, 80, 100, and 120 ppm concentrations of ethyl acetate extracts of the stem, root, and flower. The highest mortality was observed at 3% crude and 120 ppm ethyl acetate extracts after 72 hours of exposure in all the plant parts. The lowest LC50 and LC90 values of crude and ethyl acetate extracts were observed to be 0.98% and 2.23%, and 30.38 ppm and 166.99 ppm respectively in the stem of S. nigrum. Apparent dose-dependent mortality was observed as a positive correlation between mortality (Y) and concentration (X) with a regression coefficient value close to one in each case. The IR and GC-MS analyses were carried out to find out the active ingredient. Chemical characterization revealed the presence of steroidal alkaloids in the stem as a primary active ingredient, which might be responsible for larval toxicity. The active ingredient of the stem did not cause any abnormality to non-target organisms. As a whole, different plant parts of S. nigrum showed varied larval mortality, so selectively, those can be employed to prepare cost-effective insecticides to control the mosquito population.