Effect of legume diversity intercrop and varieties on population and severity of damage by foliage beetles (ootheca spp. and medythia sp.) on yields of common beans (phaseolus vulgaris l.) in western Kenya

Abstract

Bean Foliage beetles (Ootheca spp.) are a major constraint to common bean production in Kenya. Two studies were carried out during the long and short rain seasons of 2015 to determine the effect of mixtures of bean varieties and other legume species and also to investigate the effect of different bean varieties on bean foliage beetle incidence, population density and severity of damage and grain yield. Field experiments were conducted in six sites (Madola, Bujumba, Busire, Nyalara and Alupe) in Busia County and in Bondo, Siaya County. A total of 21 farmers participated in the first study and 7 in the second study. Treatments in the mixed cropping trial included Rosecoco monocrop, mixture of bean varieties and mixtures of bean varieties planted with cowpea and groundnut. Treatments in the second trial were Rosecoco, KATX56, KK8 and KATX69 bean varieties. The first trial was planted in randomized complete block design with different farmers acting as replicates. The variety trial was planted in an RCBD arrangement in each farmer’s field. The mixed cropping comprising of the three common bean varieties, groundnut and cowpea recorded the least damage severity (1.0) in both seasons compared to Rosecoco monocrop. The highest grain yield (1.73 ton ha-1) was recorded on the Rosecoco monocrop but was not significantly different from three mixtures of bean varieties together with the groundnut and cowpea (1.42 ton ha-1). Mean foliage beetle severity was significantly lowest in KATX56 (1.0) than Rosecoco bean variety (2.0). The KATX56 variety recorded significantly higher grain yield during both seasons (0.98 ton ha-1 and 0.89 ton ha-1 respectively) compared to Rosecoco variety. This study showed that mixed cropping of the bean varieties and mixtures of bean varieties, cowpea and groundnuts significantly reduced bean foliage beetle percent incidence and severity of damage and increased the yield of common beans. The choice of common bean variety influences the foliage beetle incidence, severity and the yields of the common bean.