INTEGRATED MANAGEMENT OF BLACK SCURF OF POTATO

Black scurf caused by Rhizoctonia solani Kuhn is a serious disease in the eight potato (Solanum tuberosum L.) production agro-ecological zones of Pakistan. The management of this disease problem is difficult by single control measure because of its soil-borne nature and high degree of survival of this fungus. Therefore, control measures namely chemical, biological and cultural were first investigated individually and later on the best treatment evaluated out of each study were combined in the integrated disease management (IDM) investigations. To study the effect of graded soil-borne inoculum in causation of black scurf, three potato cultivars (cvs.) and two advanced lines were evaluated against three soil-borne inoculum levels, 10, 15 and 20 g of R. solani AG 3 isolate CL-58 (a known aggressive isolate). The disease was evaluated based on eyes germination inhibition, sprouts killing, stem canker index, stolon canker index, black scurf disease index and yield reduction (parameters). It was found that 20 g inoculum dose /pot (8"xll ") of the fungus is the best for the disease screening. Management of disease through determining level of susceptibility in 14 potato cultivars I advanced lines was investigated by using isolate CL-58 under greenhouse conditions against the same abovementioned disease symptoms. The overall reaction of cvs. / lines to the disease ranked cv Desiree as the susceptible and cv. Cardinal and line CIP-393574-61 resistant.\ud \ud Concurrently, 26 plant extracts were also screened in vitro. for their antifungal activity against R. solani. Seed diffusates of Brassica rapa (turnip), B. napus (canola) and Allium cepa (onion) appeared significantly (P