2013 ASHS Annual Conference

Vegetables constitute a major commodity of the horticultural sub-sector in Kenya and play an important role in nutritional balance, income generation, foreign exchange earnings, and employment creation—especially among the rural smallholder communities who are the major producers. Major vegetables include tomato, Lycopersicon esculentum; cabbage and kale, Brassica oleracea; onion, Allium cepa; French beans, Phaseolus vulgaris; cucurbits; and cultivated and wild indigenous leafy vegetables. Pests and diseases are major constraints in production of vegetables. To address these constraints, the Kenya Agricultural Research Institute (KARI) and other institutions in Kenya have conducted pest management research based on identified priorities by vegetable stakeholders. The major Brassica pests include diamondback moth (Plutella xylostella), and aphids (Lipaphis erysimi, Myzus persicae, and Brevicoryne brassicae). While the diamondback moth has been adequately controlled by use of imported parasitoid, Diadegma semiclausum, aphid pest management remains a major challenge due to inadequate effect of beneficials leading to over dependence on chemical insecticides. Bacterial black rot caused by Xanthomonas campestrishas been adequately controlled through the introduction of resistant varieties.  Tomato is the most valuable local market vegetable in Kenya. Its major pests include bacterial wilt caused by Ralstonia solanacearum; Tomato yellow leaf curl virus; whiteflies, Bemisia tabaci; thrips, Frankliniella occidentalis and F. Schultzei; aphids, Aphis gossypii; mites, Tetranychus spp.; and bollworms, Helicoverpa armigera. The use of high tunnels made of insect proof netting, double doors, and foot bath for tomato and other vegetable have demonstrated adequate control of the major arthropod pests and diseases, while solarization using transparent polythene sheet for six to eight weeks controls bacterial wilt and nematodes, Meloidogyne spp. Grafting bacterial wilt susceptible commercial varieties on resistant MT56 or wild Solanum incanumrootstocks controlled bacterial wilt incidence in both high tunnel (15%) and open field (25%) compared with 90% and 88% incidence in open field and high tunnel, respectively.  In onion, use of grass mulch, black polythene mulches, and need-based pesticide application at the critical phonological onion stage for thrips control demonstrated higher efficiency and profitability in onion weed and thrips control. In French bean, IPM options include breeding rust resistant bean varieties and use of biopesticides. Despite these efforts, research gaps still exist; they call for participatory engagement of several actors along the vegetable productivity value chain to upscale and commercialize the developed technologies with improved market linkages between smallholder producer and consumer.