Distribution, Prevalence and Incidence of Potato Bacterial Wilt in Nakuru County, KENYA

A biological survey was carried out in 145 potato farms in nine divisions in Nakuru county, Kenya during the short rains between October and December 2012. The purpose of the survey was to provide comprehensive information on the distribution of bacterial wilt incidence, prevalence and contributing factors in the County. Percentage disease prevalence and incidence, and contributing factors were determined through observation and farmers’ interview respectively. Descriptive statistics were used to determine percentages and frequencies of data collected. Chi-square tests and spearman’s correlation coefficient analysis were used to determine significance of the data and examine relations between different variables respectively. Spot altitudes of the fields were recorded using Geographical Positioning System (GPS). Results showed that besides potatoes, other crops of economic importance in the area are wheat, tea, maize and beans. The average yield of potato in the nine divisions was 14.5 ton/ha. Bacteria wilt prevalence in the County varied from 100% in Bahati sub-County to 35.7% in Mauche and was found to be spread across all the sub Counties surveyed. The incidence also varied form 0 - 41% in the farms surveyed. There was a significant relationship between altitude and bacterial incidence at x² (36, N=111) =78.6, p<0.01. The Pearson’s correlation coefficient of r_s= -0.30, (n=111, p<0.01) indicated a reduction in bacterial incidence as altitude increased. The disease also reduced with an increase with the number of seasons the field was occupied by other crops besides potatoes as indicated by a chi­­ square test x² (20, N=46) =35.235, p<0.05, and the spearman’s correlation r_s= -.092, (n=46). Bacterial wilt symptoms on plants were more prevalent from the principal growth stage 6 (2 digit BBCH 60) and this is important in determination of the right stage of positive selection of mother plants for seed purpose. Major contributing factors to bacterial wilt in the region include; seed source, potato variety, lack of seed renewal, etc. Promotion of improved seed development techniques such as positive seed selection, production of mini tubers in the affected areas would improve the seed quality and give high yields. The relevant stakeholders should ensure accessibility of released varieties to all farmers and restrict seed movement to control spread of bacterial wilt. Development of cultural practices that are applicable and affordable in the specific regions and capacity building would contribute in reducing the bacterial wilt spread in the sub-Counties.