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

Abstract

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., <i>Acorus calamus</i>, <i>Hedychium spicatum</i>, <i>Lavandula angustifolia</i>, <i>Juniperus recurva</i>, <i>Juniperus communis</i>, <i>Cedrus deodara</i> and <i>Pinus wallichiana</i>, 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-β-pinene, camphene, α-dehydro-ar-himachalene and camphene. <i>A. calamus</i> oil showed promising fumigant toxicity to <i>Callosobruchus maculatus</i> and <i>C. chinensis</i> (LC₅₀ = 1357.86 and 1379.54 µL/L, respectively). A combination of <i>A. calamus</i> + <i>L. angustifolia</i> was effective against <i>C. maculatus</i> and <i>C. chinensis</i> (LC₅₀ = 108.58 and 92.18 µL/L, respectively). All the combinations of EOs showed synergistic activity. In the repellency study, <i>A. calamus</i> showed more repellence to <i>C. maculatus</i> and <i>C. chinensis</i> (RC₅₀ = 53.98 and 118.91 µL/L, respectively). <i>A. calamus</i> and <i>L. angustifolia</i> oil at 2500, 5000 and 10,000 µL/L significantly inhibited the AChE and GST enzymes in <i>C. maculatus</i> and <i>C. chinensis</i> after 24 and 48 h.