Effect of Neem Based Insecticides on Cabbage Aphid (Brevicoryne brassicae) and its Predator in the Central Rift Valley of Ethiopia

Abstract

The effect of two different rates of aqueous neem (Azadirachta indica) seed extracts (25g and 50g/l) and a commercial formulation of neem (Nimbecidine) on cabbage aphid (Brevicoryne brassicae) and predacious hover fly (Diptera: Syrphidae) was assessed at Melkassa Agricultural Research Centre and on farmer’s field at Wonji from October 2005 to January 2006. X-cyhalothrin
(Karate®) and water were included as standard and untreated control, respectively. At both locations, the highest rate of neem seed extract (50g/l) and A.-cyhalothrin resulted in lower aphid infestation. The yield losses recorded in the control viz. the best treatment was 66 % and 62 % at Melkassa and Wonji respectively. This is interpreated into 47 and 44 t/ha losses at Melkassa and Wonji, respectively. The population of hover fly counted in aqueous neem seed extract- treated plots was significantly lower than the control but higher than on -cyhalothrin treated plots showing that neem seed extract is compatible with the biocontrol agents.