Extracts from Hyptis suaveolens (L.) Poit. and Tephrosia vogelii Hook.f leaves as maize grain protectants against Larger Grain Borer, Prostephanus truncatus (Horn)

Abstract

The Larger Grain Borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is an important pest of maize in Nigeria. Botanical pesticides contain secondary metabolites that are useful in pest control and thus aid in agricultural pest management. The study examined the bioactivities of ethanolic and aqueous extracts of leaves of each Hyptis suaveolens and Tephrosia vogelii on LGB in stored maize. The extracts of H. suaveolens and T. vogelii leaves were applied at the rates of (0.05, 0.1, 0.2, 0.3 and 0.5ml/10g of maize grains) at dosage level and (2.5, 5.0, 7.5, 10.0, and 15.0%) at concentration level and were replicated 3 and 5 times respectively. Results showed the potency of the tested botanicals to be dose dependent. The extracts of H. suaveolens and T. vogelii leaves were found to be toxic to P. truncatus. The two extracts were observed to be toxic to P. truncatus, increased mortality, improved repellence, inhibited reproduction, caused grain damage and weight loss on stored maize at the highest dose and concentration. The results suggest that leaf extracts of H. suaveolens and T. vogelii were effective as toxicants and grain protectants against Larger Grain Borer and can be used in Integrated Pest Management (IPM) practices