Fumigant effect of some essential oils against pulse beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Bruchidae).

A fumigant toxicity tests were performed by using airtight plastic jars, in which five small glass tubes with perforated lids containing 20 cowpea seeds and four newly emerged Callosobruchus maculatus were placed. Filter paper impregnated with an appropriate volume (5, 10, 20, 40 µl/ml) of the oils were attached to the lower surface of the jar lid. Mortality counts were made at 6, 12, 24 and 48 h after treatment. For ovicidal activity, seeds having 20 eggs altogether were put in a glass vial and the treatments were followed as mentioned earlier. After 48 h of exposure the seeds with eggs were transferred and ovicidal activity was calculated based on the adult emergence. Among the essential oils tested, five oils, viz. camphor, eucalyptus, nutmeg and rosemary showed 100 % mortality even at lower dosages (5 µl) when adults were exposed for 48 h.Onthe other hand, seven oils showed 100% mortality at higher concentration (40 µl). Ovicidal activity revealed that 9 oils showed good activity against C. maculatus at higher concentrations. Among them four oils, viz. camphor, eucalyptus, rosemary and wintergreen showed 100 % egg mortality. In this work, it can be concluded that camphor, eucalyptus, nutmeg, rosemary, wintergreen oils showed very good fumigant and ovicidal activity. However, the possibility of utilising these plant oils to control C. maculatus in storage conditions may warrant further investigation. [ABSTRACT FROM AUTHOR]