Larvicidal and pupicidal efficacy of alocasia macrorrhiza (l.) schott (araceae) leaf extract and bacterial insecticide, bacillus thuringiensis israelensis against the malarial vector, anopheles stephensi liston (diptera: culicidae)

Durga Devi, G and Murugan, K

Objective: To evaluate the larvicidal and pupicidal potential of the methanolic extracts from Alocasia macrorrhiza (A. macrorrhiza) plant leaf against malarial vector Anopheles stephensi (A. stephensi) mosquitoes at different concentrations ( 60, 120,180,240 and 300 ppm).
Methods: Alocasia macrorrhiza was collected from the area of around Bharathiar University, Coimbatore. The dried plant materials were powdered by an electrical blender. From each sample, 50 g of the plant material were extracted with 300 mL of methanol for 8 h in a Soxhlet apparatus. The extracts were evaporated to dryness in rotary vacuum evaporator to yield 122 mg and 110 mg of dark greenish material (residue) from Alocasia macrorrhiza. One gram of the each plant residue was dissolved separately in 100 mL of acetone (stock solution) from which different concentrations, i.e., 60, 120,180,240 and 300 ppm were prepared.
Results: Larvicidal activity of Alocasia macrorrhiza exhibited in the first to fourth instar larvae of the A. stephensi, and the LC 50 and LC 90 values were larval and pupal mortality of A. stephensi (first to fourth instars and pupae) after the treatment of Alocasia macrorrhiza at different(60 to 300 ppm). 32.7 % mortality was noted at I-instar larvae by the treatment of Alocasia macrorrhiza at 60 ppm, whereas it has been increased to 98.4 % at 300 ppm of Alocasia macrorrhiza leaf extract treatment. The LC50 and LC90 values were represented as follows: LC50 value of I instar was 126.55 ppm, II instar was 143.19 ppm, III instar was 165.10 ppm, and IV instar was 186.13 ppm. The LC90 value of I instar was 278.81 ppm, II instar was 327.47 ppm, III instar was 380.01 ppm, and IV instar was 421.04 ppm. The LC50 value of pupae was 205.68 ppm, and the LC90 value of pupae was 456.92 ppm.
Conclusions: The present study indicates that the phytochemicals derived from Alocasia macrorrhiza plant leaf extracts are effective mosquito vector control agents and the plant extracts may be used for further integrated pest management programs