Verticillium albo-atrum carried by certified seed potatoes into Washington and control by chemicals

Fifty-one percent of 110 lots of certified seed potatoes from 10 states and Canada sampled in 1968 and 30% of 134 lots from nine states and Canada sampled in 1969 were infected withVerticillium albo-atrum. Fortyone percent of the 1968 lots and 13% of the 1969 lots carried soil infested with the fungus on tuber surfaces. The dark mycelial type ofV. albo-atrum was found infecting tubers more often than the microsclerotial type, however, high propapgule populations of the microsclerotial type were present on tuber surfaces in the soil of infested lots. Over 24% of the isolates ofV. albo-atrum infecting and infesting tubers from lots of seed potatoes were pathogenic to eggplant var. Black Beauty. Captan^®, household bleach (5.25% sodium hypochlorite), Polyram^®, Orthocide^®, and Semesan Bel^®, were effective in preventing germination of the fungus in small amounts of soil such as might be carried by infested tubers. Liquid treatments were more effective than dusts.