Bioactivity of leaf volatiles of Azadirachta indica A. Juss. and Murraya koenigii Spreng. against Sitophilus oryzae L. (Coleoptera: Curculionidae)

Abstract

Repellent activity, fumigant and contact toxicities of leaf volatiles of Azadirachta indica A. Juss. and Murraya koengii Spreng. were evaluated against Sitophilus oryzae L. In the dual choice repellency test with A. indica leaf volatiles, significantly higher number of insects was repelled at doses above 100 mg, whereas volatiles of M koenigii attracted insects at 25 mg dose and repelled at 300 mg dose. In the fumigant toxicity test 100% mortality was observed at the concentration of 32.5 mg/ml, 3 days after the treatment with 2 volatiles separately. The LC* values for fumigant toxicities were 13.5 and 22.5 mg/ml for A. indica and M. koenigii volatiles, respectively. In contact toxicity test, 100% mortality was observed immediately after 48 h contact exposure of insects at concentrations of 0.375 and 0.125 mg/cm2 of A. indica and M. koenigii respectively. The respective LCS0 values were 0.12 and 0.08 mg/cm2 for A. indica and M. koenigii leaf volatiles.