Seyoum, Emiru(PhD)Gacii, Peter2021-12-132023-11-082021-12-132023-11-082000http://etd.aau.edu.et/handle/123456789/29218Studies on the relative importance of the three known species of cabbage aphids (Brevicoryne brassicae (Linneaus), Myzus persicae (Sulz) and Upaphis erysimi (Kaltenbach)) and their parasitoid complex in Kenya were carried out. The studies involved farmers' fields' surveys and interviews and also field experiments conducted at the Jomo Kenyatta University of Agriculture and technology (JKUAT) Research and Production Department land and in a farmer's field at Limuru. Gloria F1 hybrid was sown at JKUAT while Copenhagen Market variety was sown at Limuru. The field experiments were conducted in a Completely Randomized Block Design (CRBD) involving three treatments and a control, with three repl icates each. The treatments comprised of applications of: - Lambda-Cyhalothrin (Karate; Bacillus thuringiensis Berliner (Bt.) var. Kurstaki toxin (Dipel 2x) that selectively kills Diamondback moth (DBM); A combination of the two pesticides (Karate and Bt.) and Untreated controls. Parameters included; relat ive abundance of the three species of aphids; their corresponding damage to cabbage; the number of mummies per sample; percent parasitism and the proportions of the primary- and hyper-parasitoids hatched. The parasitoid complex was constructed from the identified parasitoids. The results showed aphid counts to be higher in non karate-treated plots than in the karate-treated ones. More hyperparasitoids notably Alloxysta sp and Pachyneuron sp. than the only primary parasitoid (Diaeratiella rapae) emerged from non karate-treated plots. This might suggest that karate might have the advantage of repelling hyperparasitoids or inhibiting their emergence. Yield showed some negative correlation with aphid infestations. A combined treatment gave the best overall yield at both sites.enThesis