OCCURRENCE OF THE PEA APHID, ACYRTHOSIPHON PISUM (HARRIS) (HOMOP-TERA: APHIDIDAE) ON WILD LEGUMINOUS PLANTS IN WEST GOJAM, ETHIOPIA

Abstract

The occurrence of pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), on wild annual and perennial leguminous plants was studied at two locations (Adet and Wondata) in West Gojam, Ethiopia in 1999/2000 seasons. Annual and perennial leguminous wild or volunteer plants encountered in the study areas were closely monitored for the presence of pea aphid. The results showed that pea aphids infested annual legumes such as clover (Trifolium ruepellainum) (wild) and vetch (Vicia spp) carried more aphid load than clover. The aphid attacked more vetch in September and clover in October. From perennial legumes, pigeon pea (Cajanus cajan) was the most susceptible to attack by pea aphids and it was heavily infested and damaged in September and October. High plant density of vetch carried more aphid load than low plant density; sole stand of vetch plants suffered more damage than when grown mixed up with other crops or weeds suggesting the advantage of intercropping to reduce pea aphids.