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

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, alpha-bisabolol. The experimental units consisted of 0.8 L flasks treated with concentrations of 1.2-11.2 mu L L-of air(-1) of the essential oil of V. arborea or its major constituent applied to disks of filter paper. alpha-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 alpha-bisabolol were 5.23 and 12.97 mu L L-1 of air and 2.47 and 8.82 mu L L-1 of air, respectively. At some concentrations, the alpha-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.