Evaluation of Insecticidal Potentials of Five Plant Extracts against the Stored Grain Pest, Callosobruchus maculatus (Coleoptera: Bruchidae)

SIMPLE SUMMARY: Conventional pesticides are synthetic chemicals that are toxic, have hazardous effects on living organisms and may be carcinogenic. Pests can be controlled in an alternative way using less hazardous and more ecofriendly methods, such as using bio-pesticides. Plants based pesticides are chemicals isolated from various plants which could be used to control pests in a non-toxic mechanism. Several plants have certain bioactive compounds which could be used as alternatives to hazardous synthetic pesticides for pest control. Some beetles could damage stored grains and thus causes huge economic losses. For example, Callosbruchus maculatus is a stored grain pest which causes more than 90% damage to sored grains in a few months. Here, in this work, the insecticidal potentials of six plants, including Melia azedarach, Nicotiana rustica, Azadirachta indica, Nicotiana tabacum and Thuja orientalis, were investigated against C. maculatus. Crude extracts of these plants at different concentration were checked against C. maculatus and mortality was observed. Maximum mortality was caused by N. tabacum and N. rustica (100%) followed by A. indica (82%), whereas minimum mortality was observed in T. orientalis (64%) at 2.5%. The results of this study revealed that the extracts of these plants could be used for the control of stored grain pests. ABSTRACT: Plant based insecticides are considered among the most economic and ecofriendly chemicals for the protection of plants and stored grains. The cowpea weevil (Callosbruchus maculatus) causes more than 90% damage to sored grains in three to six months. The current study investigates insecticidal potentials of five selected botanicals: Melia azedarach, Nicotiana rustica, Azadirachta indica, Nicotiana tabacum and Thuja orientalis. They are explored at six different concentrations (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%) against C. maculatus and compared to effects of distilled water which is used as a control. Toxicities of 3%(V/V) extracts of N. tabacum, N. rustica, A. indica and T. orientalis against C. maculatus were 100%, 86.11%, 80.56% and 72.22%, respectively. Maximum mortality was caused by N. tabacum and N. rustica (100%), followed by A. indica (82%), whereas minimum mortality was observed in T. orientalis (64%) at 2.5%. Several phytochemicals, alkaloids, saponins, diterphenes, phytosterol, flavonoids and phenols were identified in N. tabacum and N. rustica, while few were present in A. indica. Phytosterol was present in greatest abundance. Saponins were only detected in aqueous extracts of N. rustica and N. tabacum. Taken together, these results indicate the utility of N. tabacum, N. rustica and A. indica as potential botanicals to control pest beetle and cowpea weevil.