Bioefficacy of plant oils applied through wooden cube impregnation against pulse beetle, Callosobruchus maculatus (F.) in green gram

Abstract

Aim: To assess the bioefficacy of plant oils against pulse beetle, Callosobruchus maculatus (F.) in green gram through wooden cube impregnation. Methodology: Bioefficacy of plant oils viz; clove, sweet flag, eucalyptus, orange, cedar wood and neem at two doses, i.e., 0.5 ml and 1.0 ml dispensed through a small wooden cube was assessed against the pulse beetle in green gram. The oils except neem are essential oils. A wooden cube impregnated with plant oil was placed over the grain surface and ten pairs of adult insects were released into each treatment. Data on oviposition, adult emergence and grain damage was recorded in each treatment. Insect mortality due to fumigant effect of plant oil at 0.5 ml per cube was also observed. Results: There was no oviposition by pulse beetles in clove, sweet flag, and eucalyptus oil treatments at 0.5 ml against the untreated control which recorded 14 eggs/100 grains. Consequently, no population buildup was observed in clove, sweet flag, eucalyptus and orange oil treatments after 120 days. A total of 2313.33 adults emerged from the untreated green gram inflicting 46.67 percent grain damage. In fumigant toxicity test, hundred per cent mortality of pulse beetle adults was observed with orange oil in 48 hr of treatment and with eucalyptus oil in 72 hr at 0.5 ml. The results indicated that the plant oils showed strong oviposition deterrence as well as insecticidal activity against the pulse beetle. Thus, application of essential oils through a wooden cube was found highly effective to keep away the pulse beetles. Interpretation: Essential oils of clove, sweet flag, eucalyptus and orange when applied through wooden cube impregnation at a dose as low as 0.5 ml showed strong oviposition deterrence and insecticidal activity against pulse beetle. The insecticidal activity of oils can be attributed to the fumigant action and can be used effectively to prevent pulse beetle infestation in grain legumes.