The soil borne pathogen Rhizoctonia solani is of increasing importance since organic seed potatoes are compulsory in organic potato production. No convincing measure to control the disease is available for organic production. The effect of a suppressive compost mixture of organic household and yard waste to control R. solani in potatoes was tested in an organic field trial at the University Kassel in 2006. The compost was directly applied at the seed tuber area. Seed tubers (variety Nicola) naturally infested with black scurf were planted in three infection classes (no, middle and high infection).
Compost amendment had a strong impact on symptoms of R. solani on tubers. The reduction of both the infestation of harvested potatoes with black scurf and the rate of tubers with deformations and dry core was significant at final harvest. Although the rate of initial infection of the seed tubers had an impact on tuber health and quality the disease was reduced up to 50% in all infection classes. These promising results en-courage increasing the research on a development of a strip application technique of composts to control the disease
