Vapor toxicity of Lavandula angustifolia (Mill) and Zataria multiflora (Bioss ) essential oils against the adults of cowpea seed beetle Callosobruchus maculatus (F.) (Coleoptera: Bruchidae )

Abstract

A key pest of cereals is the cowpea seed beetle, Callosobruchus maculatus, a bruchid that infests various stored pulses 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 much attention of many researchers. The objective of the present work was to evaluate the vapor efficiency of the essential oils extracted from the aromatic species, Avishan-e-Shirazi, Zataria multiflora and Lavender, Lavandula angustifolia on controlling the population of the cowpea seed beetle, C. maculatus. The essential oils of Z. multiflora aboveground parts and L. angustifolia flowers 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 at 29±1ºC, 55±5% RH and dark. The difference in toxicity between essential oils was made by comparing the estimates of LC50s, LC90s and probit mortality-concentration regression lines provided by POLO-PC computer software. The toxicity of both oils was significantly and positively associated with concentration and exposure time. The males were more sensitive than females. The insects were 9-10 times more tolerant to the vapor of Z. multiflora oil compared to that of L. angustifolia oil. The 24 h 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 suggested that the oils of these species especially Lavender oil can be employed as good alternatives to fumigant insecticides or other chemical synthetic compounds to protect stored pulses against the cowpea seed beetles.