Incidence and Severity of Common Bean (Phaseolus vulgaris L.) Pests in Agro-Ecological Zones and Farming Systems of Western Kenya

ABSTRACT Infestation by insect pests is a serious problem in legume up scaling activities and a threat to future production in Kenya. The survey aimed at determining incidence and severity of insect pests of common beans in different districts and agro-ecological zones of western Kenya. Foliage beetle incidence was highest in the hot and drier LM3 (72.6%) and LM4 (92.1%) zones during the long and short rains, respectively. Leaf hopper incidence was highest in LM4 (26.8%) and (59.3%) whereas bean fly incidence was highest in UM3 (12.4%) and LH1 (2.9%). Whitefly incidence was highest in LM3 (13.0%) and LM2 (17.9%) and aphid incidence was highest in LM1 (16.5%) and UM1 (40.8%). Plant bug incidence was highest in LM1 (16.5%) and LM2 (5.8%). Flower thrips incidence was highest in LM2 (20.7%) and (34.2%) in both seasons. Bean flies (7.2%) and Spodoptera (2.9%) incidences were higher during the long rains. Foliage beetle incidence (52.7%), aphids (22.6%), leaf hopper (27.9%) and flower thrips (17.8%) were higher during the short rains. Whitefly (7.9%), thrip (9.7%) incidences and foliage beetle severity (2.1) were lower on improved cultivars in LM2 areas in Homa Bay. Intercropping reduced aphid incidence (18.3%) and severity (1.3) in UM1 areas in Vihiga district. Inorganic fertiliser reduced bean fly (3.8%) and thrips (11.8%) incidences in UM1 areas in Vihiga and in LM2 areas in Siaya districts, respectively, compared with fields without fertiliser. The result is important in the development of strategies in bean insect pest management and control.