Cost: Benefit analysis of botanical insecticide use in cabbage: Implications for smallholder farmers in developing countries

Botanical insecticides based on plant extracts are not widely used as crop protectants even though they can be produced simply from locally available plants. Many studies have examined efficacy but there is a paucity of information on the cost:benefit ratio of their use compared with conventional insecticides. In the present study, crude extracts of Ageratum conyzoides (Asterales: Asteraceae), Chromolaena odorata (Asterales: Asteraceae), Synedrella nodiflora (Asterales: Asteraceae), Nicotiana tabacum (Solanales: Solanaceae), and Ricinus communis (Malpighiales: Euphorbiaceae) were compared with the synthetic insecticide, emamectin benzoate (Attack) against insect pests of cabbage in randomised, replicated field experiments during the major and minor rainy seasons of 2012 in Ghana. The cost of each treatment including material and labour was calculated and the revenue of each derived using the value of the marketable yield of cabbage. The cost:benefit ratios of sprayed treatments were derived by comparing the cost of each plant protection regime against the additional market value of the treatment yield above that obtained in the control treatment. With the exception of plots sprayed with N.tabacum, the cost of plant protection using Attack® was higher than any of the botanicals in both seasons. The highest cost:benefit ratio of 1: 29 was observed for plots sprayed with C.odorata and was followed closely by N.tabacum treatment with 1: 25 and Attack with 1: 18. In the minor season, plots sprayed with Attack had the highest cost:benefit ratio of 1: 15 and was followed closely by N.tabacum with 1: 14. Botanical insecticides differed markedly in levels of pest control and cost:benefit but some were comparable to that from conventional insecticide use whilst being produced easily from locally available plant materials and are likely to be safer to use for smallholder farmers and consumers in developing countries.