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