Insecticidal activity of Vanillosmopsis arborea essential oil and of its major constituent α-bisabolol against Callosobruchus maculatus (Coleoptera: Chrysomelidae)

Abstract

Vigna unguiculata, one of the most important legumes, mainly in underdeveloped countries, is susceptible to post-harvest losses in storage by Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae). The work evaluated the toxicity, inhibition of oviposition, instantaneous rate of population growth (r_i) and the development of fumigated C. maculatus with the essential oil of Vanillosmopsis arborea and its major constituent, α-bisabolol. The experimental units consisted of 0.8 L flasks treated with concentrations of 1.2-11.2 μL L^-1_{of air} of the essential oil of V. arborea or its major constituent applied to disks of filter paper. α-Bisabolol was quantified as 409.33 mL L^-1 of the essential oil. The development rate of C. maculatus was evaluated by daily adult counts. Oviposition was evaluated at lethal concentrations (LC₅₀, LC₂₅, LC₁₀ and LC₁). The LC₅₀ and LC₉₅ of the essential oil of V. arborea and α-bisabolol were 5.23 and 12.97 μL L^-1 of air and 2.47 and 8.82 μL L^-1 of air, respectively. At some concentrations, the α-bisabolol was more toxic to males than to females of the insect. Increased concentrations of the essential oil reduced the r_i, rate of development, oviposition, and number of eggs of C. maculatus and therefore have potential for pest control.