Eradication of potato wart disease from Maryland

Abstract

Potato wart disease, caused bySynchytrium endobioticum (Schilb.) Perc., is a disease of quarantine significance due to the production of persistent resting spores and lack of effective chemical control measures. The disease was present in limited areas of Pennsylvania, Maryland and West Virginia in 1918–1920 and was thought to have been eradicated by 1974. A recent survey in Maryland to verify eradication in that state had revealed the presence of resting spores of the fungus in one home garden in Allegany County. A subsequent delimiting soil sample survey was conducted in and around the old quarantine area in Allegany County. None of the soil samples from 176 home gardens surveyed were positive forS. endobioticum resting spores. Bioassays with susceptible potato cultivars were conducted for five consecutive years at the site from which spores had been recovered. During three of the five years, environmental conditions did not preclude development of disease, yet no symptoms were obtained. According to the USDA APHIS guidelines for eradication of potato wart disease, the spores at the Allegany County, Maryland site are declared nonviable and Maryland is considered to be free of the potato wart pathogen.