Species range and abundance of insect predators of the bean aphid, Aphis fabae Scop. (Homoptera: Aphididae) on common beans in Kenya

Abstract

The diversity and abundance of insect predators of the bean aphid, Aphis fabae Scop. (Homoptera: Aphididae) on common beans, Phaseolus vulgaris L., were evaluated in Central Kenya. Predators included species in the Orders Coleoptera, Diptera, Hemiptera and Neuroptera. Coccinellidae were the most abundant and diverse group and several species, such as Hippodamia variegata Goeze and Platynaspis capicola Crotch, had hitherto not been recorded on common beans in Kenya. Higher numbers of predators developed on beans during the short rains (up to 540/100 m2 plot) as compared to the long rain season (182/plot) of 1985. In both seasons, numbers of coccinellid larvae were high after the fourth week of bean growth. The study provides evidence of an important build-up of insect predators on beans.