Survival ofHelminthosporium solani in soil andin vitro colonization of senescent plant tissue

Silver scurf, caused byHelminthosporium solani, is considered to be a tuberborne disease of potato. The ability ofH. solani to overwinter in soil was evaluated in field studies at two locations in New York during 1992. Field plots were established at sites whereH. solani infected potatoes had been produced in 1991. Plants produced from pathogen-free tubers of four cultivars yielded tubers infected with silver scurf at both locations. Up to 61% of tubers were infected in some plots. The ability ofH. solani to colonize leaf tissue was evaluated inin vitro assays. Detached leaves of ten crops were sprayed with a spore suspension ofH. solani and incubated for 20 days.H. solani colonized and sporulated on senescent leaf tissue of alfalfa, sorghum, rye, oats, corn and wheat, and only colonized senescent tissue of rapeseed, red clover and buckwheat. No growth was observed on potato leaf tissue. These results indicate that soil survival and saprophytic ability may be important in the epidemiology of silver scurf of potato.