author(s)
Jyotika Brari and DR Thakur

abstract
Fumigant toxicity of essential oils obtained by hydrodistillation from eight plant species viz. Artemisia maritima L., Cinnamomum zeylanicum Blume, Citrus hystrix DC., Colebrookea oppositifolia Sm., Pelargonium hortorum Bailey, Rabdosia rugosa Wall. Ex Benth, Thuja occidentalis L. and Zanthoxylum armatum DC. Was tested against different immature stages of Tribolium castaneum (Herbst) and Plodia interpunctella (Hubner). 8-10 day and 18-20 day old larvae of P. interpunctella and T. castaneum were used for the bioassay. R. rugosa oil gave 80.03±5.6% mortality at 100 µl/ml followed by 65.47±2.9% mortality against 18-20 day old larvae of T. castaneum at similar concentration after 120 hrs. At the lowest concentration of 10 µl/ml R. rugosa oil produced 53.8.33±2.2% mortality for 8-10 day old larvae and a mortality of 40.55±3.9% respectively was obtained for 18-20 day old larvae of P. interpunctella after similar time period. Among eight essential oils tested R. rugosa had the highest toxicity followed by A. maritima, C. zeylanicum, Z. armatum, T. occidentalis, P. hortorum, C. oppositifolia and C. hystrix against both the insect pests. The results revealed increase in tolerance as the immature stages grow older. 18-20 day old larvae were least susceptible to all the treatments as compared to 8-10 days old larvae of both insects. Larvae of T. castaneum were found to be more susceptible for all treatments than P. interpunctella.