Influence of different coloured agronet covers on water use efficiency, insect pest populations, yield and quality of french bean (Phaseolus vulgaris l.)

Abstract

French bean (Phaseolus vulgaris L.) is among the leading export vegetables in Kenya, intensively grown by small scale farmers. Despite the economic importance of the crop, many growers are still not able to achieve maximum yield and quality due to unfavourable weather and heavy infestation by insect pests as the crop is predominantly grown in open fields. Coloured net technology is an emerging technology, which introduces additional benefits on top of the various protective functions of nettings. To determine the potential of coloured net covers in improving French bean production under tropical field conditions, this study was undertaken in the Horticulture Research and Teaching Field, Egerton University, Njoro from July to October, 2015 (trial 1) and November, 2015 to February, 2016 (trial 2). The experiment was set in a Randomized Complete Block Design (RCBD) with six treatments replicated four times. French bean „Source‟ was grown under different coloured nets (white, blue, yellow, grey, and tricolour) and control (open field). Variables measured included; water use efficiency, pest infestation, growth variables, yield components, yield and quality. Data obtained were subjected to analysis of variance (ANOVA) and means of significant treatments separated using Tukey‟s Honestly Significant Difference Test at P ≤ 0.05. French bean grown under the different coloured net covers showed relatively better growth, enhanced water use efficiency and crop performance marked by more pods and higher total yields and percentage of marketable yields compared to open field plants. Populations of silverleaf whitefly and black bean aphids were reduced under different coloured agronet covers as compared with control treatment. Growing the crop under the different coloured agronet covers substantially improved French bean marketable yields by between 97.65 – 175.17% and 28.85 – 94.42% in trial 1 and 2 respectively. Coloured nets especially light-coloured nets also hastened the rate of French bean pod maturation with the potential of reducing harvest interval. The study recommends use of the white and yellow net covers for maximizing French bean pod yield and quality.