Pantnagar Journal of Research

Abstract

Fumigant toxicity of alpha-pinene, beta-pinene, eucalyptol, linalool and sabinene was studied under laboratory condition against Rice Weevil, Sitophilus oryzae (L.) at 100,200,300,400 and 500ul/l air. The mortality of adult insects was recorded at 6, 12, 24, 48, 72 and 96 h after fumigation. The mortality of insects increased with increase in concentration of all the test chemicals and exposure time. Less than 50 per cent mortality was recorded after 6h fumigation in all the treatments even at highest dose. Exposure of insects to 500ul/l air eucalyptol, alpha-pinene and beta-pinene resulted in 96.7, 93.3 and 66.7 per cent mortality, respectively, after 12 h which increased to 100 per cent after 24h. As compared to aforementioned treatments, low toxicity was recorded in case of sabinene and linalool which showed 73.3 and 30.0 per cent mortality after 12h which increased to 90.0 and 90.00 per cent, respectively, after 24h. After 48, 72 and 96h fumigation all the treatments showed 100 per cent mortality at all the concentrations except 100 ul/l air. The present study revealed that alpha-pinene, beta-pinene, eucalyptol, linalool and sabinene were toxic to adults of S.oryzae, however, remarkable difference was noticed in their relative efficacy against this insect. Eucalyptol which killed all the insects at 200ul/l air after 24h exposure may be adjudged as most toxic followed by beta pine and alpha pinene which exhibited such high level of mortality at 300 and 400ul/l air during the same exposure. With high mortality at 100ul/l air after 24, 48, 72 and 96h exposure, linalool may be treated as more toxic as compared to sabinene. It may be concluded that all the tested monoterpenes are effective against S. oryzae and the essential oils having these chemicals may be used in the future for the fumigation of grain for its eco-friendly management.