The Relative Importance of Three Cabbage Aphid Species (Brevlcqryne Brassicae, Upaphis Erysimi ; Myzus Perslcae) and their Parasitoid Complex in Kenya

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Date

2000-05

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Addis Ababa Universty

Abstract

Studies on the relative importance of the three known species of cabbage aphids (8revicory/le brass;cae (Unneaus), Myzus persicae (Sulz) and Upaphis arysim/ (Kaltenbach» and their parasitoid complex in Kenya were carried out. The studies involved farmers' rlelds' surveys and intet"llews and also field experiments conducted at the Jorno Kenyatta University of AgricultLKe and technology (JKUAT) Research and Producti041 Department land and in a farmer's field at Umuru. Gloria Fl hybrid was sown at JKUAT while Copenhagen Market variety was sown at Umuru. The field experiments W&fe conducted In a Completely Randomized Block Design (CRBD) involving three treatmants and a control, with three replicates each. The trealments comprised of applications of: - lambda-Cyhalothrin (Karate; Bacillus /huringiensis Berliner (8t.) var. Kurstaki toxin (Dipel 2x) that selectively kills Diamondback moth (DBM); A combination or the two pesticides (Karate and Bt.) and UnlIeated controls. Parameters included; relative ablXldance of the three species of aphids; their corresponding damage to cabbage; the number of mummies per sample; pereent parasitism and the proportions of the primary- and hyper-parasitoids hatched. The parasiloid complex was constructed from the identified paras ito ids. The results showed aphid counts to be higher in !'1M karate-treated plots than in the karata-treated ones. More hyperparesitoids notably Alloxys/a sp and Pachyneuron sp. than the only primary parasiloid (Diaeraliella rapaa) emerged from non karale-treated plots. This might suggest that karate might have the advantage of repelling hyperparasitolds or inhibiting their emergence. Yield showed some negative correlation with ephid infestations. A combined treatment gave the best ov9(all yield at both sites .

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Keywords

Cabbage Aphid Species

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