Sustainable management of two key pests of cabbage, Brassica oleracea var. capitata L. (Brassicaceae), using homemade extracts from garlic and hot pepper

Cabbage, Brassica oleracea var. capitata L., is an important leafy vegetable that provides vitamins and minerals for healthy body development. However, insect pest attack is a key contributing factor to its low yield. An experiment was undertaken at the agricultural research field of Crops Research Institute, Council for Scientific and Industrial Research (CSIR), Kwadaso in Ghana, during the major seasons of 2010 and 2011 to explore the potential of homemade extracts from garlic, Allium sativum L., and hot pepper, Capsicum frutescens L., in the management of insect pests of cabbage. Emamectin benzoate (ATTACK®) and lambda-cyhalothrin (BOSSMATE® 2.5EC) were used as reference insecticides. There were ten treatments made up of three levels (10, 20 and 30 g L^-1 w/v) each of garlic, pepper, a mixture of garlic and pepper, ATTACK®, BOSSMATE® and control (tap water). The key insect pests recorded were the aphid, Brevicoryne brassicae L., and the diamondback moth, Plutella xylostella L. Generally, the efficacy of garlic and pepper was comparable to that of ATTACK®, with BOSSMATE® being the least efficacious. Pepper (20 g L^-1 w/v) and ATTACK® (1 ml L^-1 v/v) were more effective in controlling P. xylostella than the other treatments. Natural enemies encountered were the Coccinellidae, Syrphidae and Araneae. Generally, BOSSMATE® caused the greatest reduction in natural enemies' abundance, followed by ATTACK®, with the plant extracts having a mild effect on the natural enemies. Cabbage head yield was comparable among insecticide-treated plots and botanical plots with the control plots doing well in some instances. Garlic and pepper offer a significant potential for further exploration and development into affordable plant protection products for cabbage pests' management, especially in smallholder farms and backyard gardens and organic vegetable production systems.