On-Farm Evaluation of Homemade Pepper Extract in the Management of Pests of Cabbage,Brassica oleraceaeL., and French Beans,Phaseolus vulgarisL., in Two Agro-Ecological Zones in Ghana

Abstract

Cabbage, Brassica oleraceae L., and French beans, Phaseolus vulgaris L., are important vegetables grown in Ghana. However, attack by insect pests affects their quality and marketable yield. On-farm experiment was undertaken during the major rainy season of 2012 at Afari and Kpong, in the moist Semi Deciduous Forest and Coastal Savanna agro-ecological zones of Ghana, respectively, to explore the use of homemade extracts from fruit of hot pepper, Capsicum frutescens L. in the management of insect pests of cabbage and French beans. The treatments included a crude water extract from pepper fruit (20 g/l w/v), the semi-synthetic insecticide emamectin benzoate, ATTACK® (1 ml/l v/v) and tap water as a control. The dominant pests found on cabbage at both locations were the diamondback moth (DBM), Plutella xylostella (L.), the cabbage aphid, Brevicoryne brassicae (L.) and the whitefly, Bemisia tabaci (Gennadius). On French beans, the flower thrips, Megalurothrips sjostedti (Trybom), the whitefly, B. tabaci and a range of leafhoppers, Empoasca spp. were found at both locations. The cowpea aphid, Aphis craccivora (Koch) was present only at Kpong. Among the natural enemies found on cabbage at both locations were the larval parasitoid, Cotesia plutellae (Kurdjumov), the ladybird beetles, Cheilomenes spp., hoverflies and a number of spiders. On French beans, ladybirds and spiders were observed only at Kpong. Generally, the application of pepper and emamectin benzoate were effective in controlling some pests of cabbage and French beans and also conserved the natural enemies. Emamectin benzoate and pepper treated-plots had higher yields of French beans than the control plots at Afari. The potential of homemade pepper spray for pest management on smallholder farms, backyard gardens and in organic vegetable production systems is discussed.