Seasonal variation in the insecticidal action of chilli pepper (Capsicum frutescens) products on the cowpea bruchid (Callosobruchus maculatus f.) infesting stored cowpea seeds in Maiduguri, north-eastern Nigeria

Abstract

Seasonal variation in the efficacy of 0.0 (control), 1.0, 2.5 and 5.0g extracts of each of ground seed, ground rind, ground whole fruit and unground whole fruit of chilli on the reproduction of Callosobruchus maculatus were investigated during the hot (April/May; 21.1-34.7°C; 13.0-37.0% R.H.) and the cold (November/December; 20.1-24.0°C; 13.0-26.0% R.H.) dry seasons in Maiduguri. Oviposition and adult development were significantly reduced in treated seeds than the untreated control and in the cold dry than in the hot dry period. The form and dose differential efficacy responses of chilli on the depression of both fecundity and adult development in C. maculatus were in the decreasing order of ground seed > whole fruit > ground rind > unground rind and 5.0g chilli > 2.5g > 1.0g.