Status of potato bacterial wilt in Nakuru County (Kenya) and its management through crop rotation and soil amendments

Abstract

Bacterial wilt caused by Ralstonia solanacearum, is the second most damaging potato disease in tropical and sub-tropical regions causing up to 75% of crop loss and affects 77% of potato farmers in at least 10 Counties in Kenya. Lack of actual information on the distribution of bacterial wilt limits application of strategic approaches in curbing the disease in Nakuru county and other parts of Kenya. A survey was undertaken using a semi structured questionnaire and personal observation to collect data in nine Wards to establish it’s occurrence in Nakuru County. The results showed that the average yield of potato in the nine Wards surveyed was 14.5 ton/ha. Bacterial wilt prevalence in the County varied from 100% in Bahati Ward, to 35.7% in Mauche Ward. The wilt incidence in the farms varied from 0 to 41%. A biochemical analysis of R. solanacearum isolates collected from bacterial wilt infected potatoes and common weeds within the farms indicated that biovar 2 and 3 were existent in the County. Seed source, potato variety and lack of seed renewal were the main contributing factors to bacterial wilt in the County. Consequently, crop rotation and soil amendment experiments were laid out in RCBD design in plots of 3m x 3m in Egerton University, Njoro and KALRO, Kabete to evaluate their effect on bacterial wilt. The results indicated that pre-cropping potato with spring onion and barley resulted to significantly lower wilting incidence in potato with a grand mean of 8.3% across the two locations. Potato- Dolichos lablab-Potato and Cabbage-Dolichos lablab- potato had the highest potato yield of 19.9 tons/ha and 19.7 tons/ha respectively. In the long season crops experiment, potato planted after Desmodium intortum recorded the lowest mean wilt incidence (18.7%) and highest mean yield (16.2 tons/ha). The soil amendment results showed that NPK + Black majik is a promising combination of organic and inorganic fertilizer which can be used to increase yields in the short term and also improve reduce bacterial wilt incidence. Black majik + NPK, cow manure, Takataka compost and neemgold significantly reduced the wilt incidence at Egerton site compared to the negative control (no amendment) F (7,128) = 2.830, P<0.05. Sourcing for clean seed from approved seed potato dealers should be encouraged among farmers. Rotations involving spring onion with the locally grown cereals can be utilized in curbing bacterial wilt. Reinforcing inorganic fertilizers with organic amendments is essential in the short term realization of high yields and improving soil health. This study provides comprehensive information on the status of bacterial wilt in Nakuru County and also offers affordable and applicable measures to farmers in curbing bacterial wilt.