SCREENING CITRUS ROOTSTOCK/SCION COMBINATIONS FOR TOLERANCE TO MAJOR PESTS AND DISEASES IN NORTH RIFT KENYA

Abstract

Most farmers in North Rift Kenya have abandoned their citrus orchards due to low yields caused by diseases and insect pests. Very few farmers are starting new citrus orchards because of lack of suitable planting materials and high costs of production. Black spots, greening disease, aphids and scales account for a large proportion of the disease and pest control expenditure. Neglected or old trees are more susceptible to diseases and insect pests than newly established, healthy and vigorous ones. The use of specific root stocks for commercial citrus production has several advantages such as control of tree size, early fruit production and tolerance to pests and diseases. The objective of the trial was to screen for better disease and pest tolerant rootstock/scion combinations to be recommended to farmers. 25 rootstock/scion combinations were screened at KARI Kitale in a randomized block design replicated 3 times. All trees were subjected to similar recommended agronomic practice with minimum spraying and data collected on plant vigour, pest and disease incidence and yields. Results for 3 years 2006 to 2008 indicated the best rootstock/scion combinations in terms of yield and pest/disease tolerance as: ‘Rough Lemon’/‘Washigton Navel 102’, ‘Troyer Citrange’/‘Washington Navel 39’, ‘Citrumello 4475’/‘Washington Navel 205’, ‘Citrumello 4475’/‘Washington Navel 216’ and ‘Carrizo Citrage’/‘Washington Navel 205’. From this study we recommend that, the pest and disease tolerant rootstock/scion combinations be combined with the recommended spraying regime as an integrated pest management strategy for Citrus. It is important to verify these technologies in other agro-ecological zones and scale it up for more adoption and increased production.