Lavandula dentata Essential Oils: A Bio-Insecticide for an Agroecological Approach to Protecting Chickpea Seeds against Callosobruchus maculatus

Abstract

One of the most severe pests of legume seed is the chickpea weevil, Callosobruchus maculatus (C.m), which attack chickpea seeds (Cicer arietinum). The fight against this insect pest has mostly been limited to chemical control with its attendant environmental and health effects. The pest has also developed resistance to the chemical pesticides. The present study therefore aim to evaluate the insecticidal effect of Lavandula dentata (L.d) Essential oil (EO) on adult insects of C.m, and also to assess the impact of the insect infestation and EO treatment on chickpea seed quality. L.d EO was applied by fumigation at doses of 1, 5, 10, 20 and 40 µL/L of air to 100 g of chickpea seeds. The mortality of the insects was determined by probit analysis after 24 h exposure. The impact of the insect infestation and EO treatment on the chemical composition of chickpea seeds were also assessed. The constituents of the essential oil were determined by GC-MS analysis. L.d EO had significant insecticidal effect on the adult insects of C.m, even at low concentrations. Results from the probit analysis showed that L.d EO had LC50 of 19.43 µL/L air against C.m. The infested seeds were severely damaged with significant effect on their chemical composition and reduction in their nutritional quality. Fumigation with L.d EO did not significantly affect the chemical composition of the chickpea seeds. Linalool (35.62%) was identified as the major constituent of L.d EO. L.d EO could therefore serve as a source of biopesticides against chickpea weevil.