Association of white rot (Sclerotium cepivorum) of garlic with environmental factors and cultural practices in the North Shewa highlands of Ethiopia

Field surveys were conducted in North Shewa highlands, Amhara state, Ethiopia during 2003 and 2004 main cropping seasons to determine the distribution, prevalence and the association of garlic white rot (Sclerotium cepivorum) incidence with environmental factors and cultural practices. In both years a total of 385 garlic fields were surveyed in four districts, and 96.6% of the fields were infested with white rot. Disease incidence varied among districts and between years, altitude range, soil type and field management practices. The mean disease incidence in 2 years ranged from 21% in Lalo Mama Mider to 42% in Basona and Werena district, where it was significantly higher. The incidence in 2004 cropping season was higher by 37.28% than in 2003. Logistic regression was used to analyse the association of white rot incidence with environmental factors and cultural practices as independent variables. District, cropping year, soil type and weed management practices were significantly associated with white rot incidence in a multiple variable model. Higher incidence of white rot was significantly associated with Basona and Werena district. Lower incidences had a high probability of association with Angolela and Asagirt and Lalo Mama Mider (2003) cropping year and good weed management practices. In a reduced multiple variable model, year and weed management practice were significantly associated with lower white rot incidence. In garlic intercropped with Brassica there was very low disease incidence. The survey revealed high occurrence and distribution of white rot in the study area and effective and feasible management options need to be developed.