Evaluation of selected botanical aqueous extracts against cabbage aphid (Brevicoryne brassicae L. (Hemiptera: Aphididae) on cabbage (Brassicae oleraceae L.) under field condition in Kobo District, North Wollo, Ethiopia

Cabbage is one of the most important vegetable crops under cultivation throughout the world, especially in Africa including Ethiopia. Cabbage aphid is a sap sucking insect pest that damage cabbage. Growers use synthetic chemicals to control cabbage aphids. The aim of this study was to evaluate the efficacy of Azadirachta indicae, Otostegia integrifolia and Crinum ornatum aqueous extract against cabbage aphids. The field experiment was carried out at Kobo agricultural research sub-center from December 2016 to April 2017. The experiment was conducted in a Randomized Complete Block Design (RCBD) with 21 treatments along with standard check and untreated control and three replications. Four applications of extracts were applied at the rate of 2.5,5 and 7.5% solely and in combinations. The study revealed that effects of botanicals on aphid mortality, infestation level, area of cabbage leaves, damage of leaves, cabbage head formation, estimation of the yield and economic values. All botanical treatments were toxic against cabbage aphids. Among botanicals, neem and crinum at 7.5% concentration provided maximum cabbage yields that were comparable with dimethoate 40% E.C. Further studies should be conducted on effectiveness of these botanicals in different seasons. Key words: Cabbage aphid, plants aqueous extract, efficacy.