Potato black scurf, production practices and fungitoxic efficacy of rhizoctonia solani isolates in hilly areas of gilgit-biltistan pakistan

Potato is the main cash crop of Gilgit-Baltistan in particular of buffer zone of Central Karakorum National Park (CKNP). There are many biotic and abiotic threats to its production. Amongst them the black scurf disease caused by Rhizoctonia solani is the major constraint. In order to assess black scurf of potato a comprehensive survey was carried out in four main valleys of the region consisting of 24 villages. The survey revealed that valley wise mean disease prevalence was high in Bagrote (63.85+-9.06) and low in Haramosh (45.4+- 14.62). Maximum mean disease incidence and severity were recorded in Hoper valley while least disease incidence appeared in Haramosh and severity in Bagrote valley. Production practices as risk factor were assessed through a questionnaire. The majority of farmers performed activities in field that were supportive to the black scurf epidemics, such as, use of pits for storage of late harvested potato tuber for growing in next season, table potato, lack of general awareness about black scurf, not maintaining proper depth of sowing, irrigation, harvesting time and crop rotation. In vitro efficacy of three fungicides at different concentrations i.e. 50, 100, 150 and 200 ppm were tested against Rhizoctonia solani isolates. Results indicated that increase of fungicide concentration significantly inhibited the mycelial growth of respective isolates. However, sensitivity reaction of each of isolates against each fungicide was also differential. Fungicide ridomil gold and mencozeb showed more toxic effect against the fungus compared to vitavax. (author)