Abstract
The cowpea weevil, Callosobruchus maculatus is the one of the most destructive pests of the dried seeds including cowpea, chickpea, lentil, mung bean and broad bean. In the last few decades, the use of environmental friendly insecticides, particularly plant-based compounds, has attracted attention of many researchers. The objective of the present work was to evaluate the fumigant toxicity of the essential oils extracted from the aromatic species, Zataria multiflora and Lavandula angustifolia on the cowpea weevil, C. maculatus. The essential oils from Z. multiflora and L. angustifolia were extracted using a Clevenger apparatus. Bioassays were conducted on both sexes of one-2 day old C. maculatus adults within the enclosed 27 ml glass vials under 29±1ºC, 60±5% RH and dark condition. Differences in toxicities between essential oils were made by comparing the estimates of LC50s, LC90s and probit mortality-concentration regression lines provided by POLO-PC computer software. The toxicities of both materials were significantly and positively associated with concentration and exposure time. The males were more sensitive than females. The insects of both sexes were 9-10 times more tolerant to the extract from Z. multiflora comparing to that from L. angustifolia. The 24h LC50 values of Z. multiflora oil were 329 and 562 µlL-1 and the counterpart values of L. angustifolia oil were 34 and 54 µlL-1 for males and females, respectively. The results showed the essential oils from L. angustifolia can be a good candidate for more and practical assays.

Key words: Cowpea, Essential oils, Fumigant toxicity, L. angustifolia, Stored product pests, Z. multiflora