HPIPM:Potato Silver Scurf

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

Silver scurf is caused by the fungus Helminthosporium solani, and probably occurs worldwide. The disease is most severe when tubers are stored for long periods of time. The pathogen is generally introduced into a field on infected seed pieces, where spores of the fungus wash down onto and directly penetrate daughter tubers. H. solani can also overwinter in soils and infect both young and old tubers. The pathogen can continue to grow, sporulate, and spread in storage. The pathogen can survive between potato crops saprophytically on crop debris and organic matter, but is not known to infect other hosts.

Plant Response and Damage

Silver scurf symptoms begin as tan to gray, circular lesion that form on the periderm, generally at the stolon end of tubers. When moist, lesions have a silvery appearance. Lesions eventually spread over large areas of tuber, and develop a sooty appearance where the fungus produces spores (conidia). As symptoms progress in storage, parts of the periderm may slough off. The disease is most severe on white and red-skinned varieties, but is also important on russet-skinned varieties. Silver scurf can increase tuber shrinkage in storage because of increased water loss, as well as reduce marketability and seed quality.

Biological Control

No biological control practices have been developed for silver scurf.

Cultural Control

Plant only high quality seed free from the silver scurf pathogen. Practice crop rotation to reduce soilborne inoculum. Avoided delaying harvest, as silver scurf increases with time from crop maturity. Store tubers at the lowest temperature and relative humidity possible for the target market. Provide adequate ventilation to reduce condensation and dead air spaces. Thoroughly clean storage sheds with a disinfectant before storing tubers. If possible, market more severely affected fields earlier, as silver scurf losses increase in storage.

Chemical Control

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.