Phytochemical and insecticidal properties of some botanical extracts against the lesser grain borer, Rhyzopertha dominica F. (Coleoptera: Bostrichidae)

Abstract

Experiments were conducted in postgraduate laboratory of the Department of Biology of Umaru Musa Yar’adua University, Katsina (UMYUK) Nigeria, to analyze phytochemical properties and assess insecticidal effects of acetonic leaf extracts of Euphorbia balsamifera, Lawsonia inermis and Mitracarpus hirtus against Rhyzopertha dominica F. To analyze the phytochemicals of the test plants, preliminary tests were conducted to determine secondary metabolites while Gas Chromatography Mass Spectrum (GC-MS) was carried out to identify various active compounds present in the botanical extracts. Effects of the treatments on adult mortalities against R. dominica, adult emergence and grain weight losses were also determined. To determine percentage mortalities of R. dominica at 7 days after treatment (DAT), acetonic extracts of the botanicals at the concentrations of 6.25, 12.50, 25.00, 50.00, 100.00 mgml-1 and permethrin powder at 11.20 mg/20 g were applied to 20 g of sorghum grains in different plastic bottles. None of the extracts or permethrin powder was added to the control. The experiment was arranged in a completely randomized design (CRD) and replicated three times. Findings of the study revealed the presence of alkaloids, carbohydrate, phytesterols, phenolic compounds, flavonoids, saponins, tannins and cardiac glycosides in the botanical extracts. The plant extracts resulted in adult mortality of R. dominica which ranged from 16.67 to 63.33% within 7 days after treatment (DAT). No adult emergence was observed in all the treated grains. Also, grain weight losses of the treated sorghum varied from 3.92 to 6.63%. Acetonic extracts of the botanicals could therefore be utilized to reduce R. dominica infestations in stored sorghum.