Phytochemical composition and insecticidal efficiency of three extracts of Allophylus africanus leaves against Callosobruchus maculatus (Coleoptera, Bruchidae)
摘要
The methods mostly used to limit post-harvest losses in stocks are generally synthetic insecticides. These insecticides, although effective, cause a lot of problems for human health such as cancer, kidney failure and even for the environment in terms of pollution. However, the use of biopesticides does not cause health problems or any harm to consumers or the environment. The present study aims to develop an effective method for preserving seeds of Vigna unguiculata (Linne.) using plant extracts. To tests this, extracts of Allophylus africanus leaves were prepared using hexane, aqueous, and methanol solvents, and their insecticidal activities were assessed. The tests were carried out under laboratory conditions. Assays releasing 20 one-day-old adults of C. maculatus into jars containing heathy cowpea seeds (Lori variety) treated with each leaf extract. These tests simulated postharvest conditions typically observed by farmers. The effect of the different extracts on mortality, production of F1 offspring and reduction in damage by C. maculatus during four months of storage were also determined. Compared to control samples, all A. africanus extracts caused significant mortality, reduced F1 offspring, and limited damage caused by C. maculatus.The hexane extract was more active and caused, at the minimum dose of 2 g/Kg and on the first day of exposure, mortality of around 39%, and a reduction in F1 offspring of 65.71% and complete seed protection for 4 months of storage. The aqueous extract was the least effective, with a maximum mortality of around 27%. In contrast, the methanol extract exhibited 30% mortality on the first day of exposure at a minimum dose of 2 g/kg. By the fifth day of exposure at a minimum dose of 2 g/kg, mortality rates reached approximately 91% for the hexane extract, 80% for the methanol extract, and 76% for the aqueous extract. At a maximum dose of 12 g/kg, all extracts achieved 100% mortality by the fifth day.