INTEGRATING HOST PLANT RESISTANCE, SEED DRESSING AND EARTHING –UP ON MANAGEMENT OF BEAN FLY (Ophiomyia spp., Diptera: Agromyzidae) ON COMMON BEANS (Phaseolus vulgaris L.) IN TRANS-NZOIA COUNTY.

Abstract

Common beans are among the important food security crops in Trans-Nzoia County. Its yield is however low due to insect pest damage with the major insect pest contributing to this yield loss as bean fly. The objective of this study was therefore to improve bean yields in Trans-Nzoia by managing the bean fly through use of Integrated Pest Management strategies. A survey was conducted to determine bean production practices that influence bean fly infestation by use of a questionnaire administered to ninety farmers within three divisions’ in each of the three Sub counties of Trans-Nzoia, Cheranganyi (LH3), Central (UM4) and Kwanza divisions (LM4). The occurrence of bean fly across the three Agro ecological zones (AEZs) was also determined through farm sampling on 45 farms during the time of survey. The efficacy of integrating host plant resistance (KK8 as the resistant variety and Rosecoco the susceptible), seed dressing and earthing up study was done experimentally in the field in Kaplamai through cropping during the short rain season of 2011 and long rains of 2012. The design was a 2x2x2 factorial in a randomized complete block design. Analysis of variance, frequencies and multiple comparisons for the survey and occurrence data was done using SPSS whereas ANOVA for the field data was done using Genstat package at p≤0.05 and mean separation by LSD. The survey results showed that 77% of the farmers grew susceptible bean varieties, 56% use own farm saved seed. Forty six percent of the farmers were not able to identify bean fly symptoms and hence could not control it. Bean fly occurred in all the Sub counties surveyed and the prevalence was high (82.2%). The incidence was significantly different between the three divisions representing the agro ecological zones. It was high in LM4 (61.9%) and lowest in LH3 (48.7%). The larvae and pupae numbers were higher in KK8 and Rosecoco only treatments but lower when KK8 and Rosecoco were earthed. Integrating KK8 with seed dressing and earthing led to reduction of larvae and pupa leading to a significantly (p≤ 0.05) higher yield than Rosecoco earthed up and seed dressed. There was significant and negative correlation between bean fly pupae and yield. In conclusion therefore, bean fly occurs in Trans-Nzoia and the bean varieties grown by farmers are susceptible to this pest. Farmers’ knowledge on bean fly is inadequate. Integrating pest management components leads to lower larval and pupae numbers and leads to increased yields. Therefore farmer education and adoption of IPM technologies can reduce infestation of bean fly and hence increase bean yields.