Skip to main content

U.S. flag An official website of the United States government

Animal and Plant Health Inspection Service
U.S. Department of Agriculture
USDA FAQ's and resources about coronavirus (COVID-19).  LEARN MORE

Potato Wart

Potato Wart: A Fungal Disease of Tubers

This soil borne disease of potatoes is caused by a fungus called Synchytrium endobioticum. The disease appears mainly on stolons and tubers. Symptoms on above ground growth are not often visible. Young potato Warts are white in color, soft and pulpy in texture darkening and decaying as they age.

Synchytrium endobioticum loves wet conditions. It produces a thick walled structure known as a winter sporangium which can remain viable for up to 30 years. It can survive at depths of 50 cm in the soil. In spring, at high temperature and moisture, overwintering sporangia germinate to release mobile zoospores which infect suitable host cells. The infected plant cells swell, divide and surround the dividing zoospores resulting in the wart.

Infected seeed tubers, infected soil, machinery and implements used in infested potato fields and potato cultivation, footwear, and manure from animals that have fed on infested tubers can spread this disease.

Pest Management

Pest status of Synchytrium endobioticum

S. endobioticum is considered a federal quarantine pest and is not known to occur in the United States. This pathogen is also a Select Agent for the United States.  Samples suspected to be positive for S. endobioticum must be handled according to the Select Agent Program requirements. Refer to the below links for more information about the Federal Select Agent Program and regulations:

Federal Order

Life Cycle


Complementary Content