Response of Kenyan varieties of common bean, Phaseolus vulgaris L., to infestation by Aphis fabae Scopoli

Abstract

Common bean, Phaseolus vulgaris L., is the most widely grown legume in Kenya. The black bean aphid, Aphis fabae Scopoli, is a sporadic but serious pest of beans, causing significant yield losses in Kenya mainly during the short rainy season. Growing resistant and tolerant bean varieties is the most sustainable method for controlling the aphid, but information on varietal resistance is lacking. Studies were conducted on the varieties grown by Kenyan farmers to identify which are resistant or tolerant to the aphid during the short rainy seasons of 2002/03 and 2004/05. Ten varieties were evaluated in a randomized complete block design. Dimethoate (insecticide) kept the control, which comprised the entire ten varieties, aphid-free. Bean variety significantly affected aphid infestation in 2002/03 but not in 2004/05. Significant yield reduction as a result of aphid infestation was observed in five varieties in 2002/03 and all but one in 2004/05. Correct selection of varieties to grow during the short rainy season could therefore lead to high yields of common beans.