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First Report of Sweetpotato Scurf Caused by Monilochaetes infuscans in Italy

In the last few years, in the Treviso area, the incidence and severity of a sweetpotato (Ipomoea batata) disease has increased to become a serious economic threat to this crop. The symptoms are small, dark brown to black spots on the surface of fleshy storage roots that under high relative humidity coalesce to completely cover the root surface. Affected roots may also develop small cracks and shrink in storage. In the past, the same symptoms were observed, but the low incidence of the disease did not cause significant economic losses, and therefore it was not considered worthy of investigation. In August 1998, an investigation was initiated to determine the causal agent of the disease and to provide growers with effective control strategies. Since the symptoms were similar to those incited by Monilochaetes infuscans, agent of sweetpotato scurf (1), samples of roots were collected and examined for the presence of the pathogen. Even though it is difficult to isolate, M. infuscans was consistently present in infected tissues. In pure culture on potato dextrose agar the pathogen formed typical, raised, domelike, dark gray to black colonies. Conidiophores were brown to black, unbranched, and support straight or curled chains of hyaline conidia. Traditional cultivation methods that ignore sanitary conditions probably caused the gradual increase in the incidence and severity of the disease. Sweetpotato scurf is common in the U.S., Japan, and some Pacific islands, but it has not been previously recorded in Italy.

Reference(1): C. A. Clark and J. W. Moyer. 1988. Compendium of Sweet Potato Diseases. American Phytopathological Society, St. Paul, MN.