Effects of Grafting and High Tunnel Tomato Production on Pest Incidence, Yield and Fruit Quality in Smallholder Farms in Central Kenya

Abstract

Tomato, (Solanum lycopersicum L.) is one of the most valuable local market vegetable in Kenya. Production of the crop is constrained by abiotic and biotic stresses. The 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. To address these constraints, tomato grafting and use of high tunnels was evaluated in collaboration with smallholder tomato growers in Kirinyaga County. The aim of the trials was to compare grafted with un-grafted tomato and high tunnel with open field production on pest incidence, yield and fruit quality. The treatments included tomato seedlings of a common variety Onyx, grafted on a bacterial wilt resistant MT56 and ungrafted Anna Fl hybrid. The tomato crops were simultaneously grown in the high tunnel and open field for two seasons in a two-factor randomized complete block design. Results showed that tomato grown in the open field had higher infestation of white flies (P<0.05), thrips and aphids than tomato grown in the high tunnel where no aphids and very slight white fly and thrips infestations were recorded. Grafting the bacterial wilt susceptible var. Onyx on Mt 56 resulted in lower disease incidence in both high tunnel (15%) and open field (25%) compared to 90% and 88% disease incidence in the un-grafted Onyx in the open field and high tunnel respectively(P<0.05). There was no difference in disease incidence between the production systems (P<0.05). Higher yields were recorded from high tunnel crop than the crop in open field. Tomato in the high tunnel had superior quality in terms of peel thickness, percent brix and vitamin C.