Insecticidal and Detoxification Enzyme Inhibition Activities of Essential Oils for the Control of Pulse Beetle, Callosobruchus maculatus (F.) and Callosobruchus chinensis (L.) (Coleoptera: Bruchidae)

Pulse beetle is the most harmful pest attacking stored grains and affecting quality and marketability. Continuous use of chemical-based pesticides against pulse beetle led to the development of insecticidal resistance; essential oils (EOs) can be an effective natural alternative against this pest. The main objective was to study the chemical composition of seven EOs viz., Acorus calamus, Hedychium spicatum, Lavandula angustifolia, Juniperus recurva, Juniperus communis, Cedrus deodara and Pinus wallichiana, their insecticidal and enzyme inhibition activities against pulse beetle. The primary compounds present in these EOs were cis-asarone, 1,8-cineole, linalyl isobutyrate, 2-beta-pinene, camphene, alpha-dehydro-ar-himachalene and camphene. A. calamus oil showed promising fumigant toxicity to Callosobruchus maculatus and C. chinensis (LC50 = 1357.86 and 1379.54 mu L/L, respectively). A combination of A. calamus + L. angustifolia was effective against C. maculatus and C. chinensis (LC50 = 108.58 and 92.18 mu L/L, respectively). All the combinations of EOs showed synergistic activity. In the repellency study, A. calamus showed more repellence to C. maculatus and C. chinensis (RC50 = 53.98 and 118.91 mu L/L, respectively). A. calamus and L. angustifolia oil at 2500, 5000 and 10,000 mu L/L significantly inhibited the AChE and GST enzymes in C. maculatus and C. chinensis after 24 and 48 h.