Abstract
French bean (Phaseolus vulgaris L.) is important in the socio-economic farming systems of East and Central Africa. It is a crop with great potential for addressing food insecurity, income generation and poverty alleviation in the region. Enhanced French bean productivity is hindered by a number of biotic and abiotic constraints as the crop is predominantly grown in open fields. The crop is mostly grown under irrigation and cannot withstand prolonged dry spells. Farmers rely heavily on insecticides to control insect pests. This increases the risk of rejection of their produce due to stringent maximum residue levels (MRLs) in export markets. This study was undertaken in the Horticulture Research and Teaching Field, Egerton University, Kenya to determine the potential of coloured net covers in improving French bean water use efficiency and insect pest exclusion. 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; pest population, fresh pod yield, total plant biomass, leaf relative water content (LRWC) and water use efficiency for plant growth (WUE DW). Covering French bean with different coloured net covers reduced the numbers of silverleaf whitefly and black bean aphids. Coloured net covers enhanced crop performance marked by higher fresh pod yield and total plant biomass as well as improved LRWC and WUE DW of the crop. Results of this study present the potential of coloured net covers to be used as part of integrated French bean management programme(s) to reduce insect pest population and pesticide application while enhancing water use efficiency and crop performance under tropical field conditions.
Highlights
French bean (Phaseolus vulgaris L.) is of primary importance as a source of income, nutrition and food security among smallholder farmers in East and Central Africa (ECA) region (Musaana, Ugen-Adrogu, & Mawejje, 2015)
Aphids: Growing French bean under the different coloured agronet covers reduced the number of aphid population on the crop compared to open field production (Table 1)
Plants grown under the yellow and tricolour net covers had significantly lower aphid population compared with the control plants by 49 and 63 Diammonium phosphate (DAP) while plants covered with the white net had significantly lower aphid population than the control plants by 63 DAP
Summary
French bean (Phaseolus vulgaris L.) is of primary importance as a source of income, nutrition and food security among smallholder farmers in East and Central Africa (ECA) region (Musaana, Ugen-Adrogu, & Mawejje, 2015). French bean is primarily grown for export with a small quantity consumed in the domestic market (HCD, 2014). In Kenya, the crop accounts for 52% of the value and 61% of the volume of total vegetable exports. In 2013, Kenya exported 31,974 metric tons (MT) of French beans representing 42% increase over the volumes exported in 2012 (HCD, 2014). The yield for French bean ranges between 8 and 10 tonnes per hectare, with high yields of more than 14 tonnes per hectare recorded in China, USA and Latin America (CIAT, 2006). The average yield in smallholder farms in ECA is low, ranging between 4 and 8 tonnes per hectare (Kimani, van Rheenen, Mathenge, & Ndegwa, 2004)
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