Potato pink rot is a water mold or oomycete disease of potato tubers caused primarily by Phytophthora erythroseptica. The soilborne pathogen causes darkened, water-soaked lesions with defined margins near the stem-end of the tuber, and is often identified by the characteristic pink/salmon color and ammonia-like odor of a potato cut and exposed to air after 20-30 minutes. Potato vines can also appear stunted or wilted later in the season, with noticeable leaf yellowing and drying as the wilt moves up the stem.
Source: Infested soil (up to 7 years), infected tubers in storage
Spread:
- In Field: Direct contact with infested soil, swimming zoospores during wet conditions
- Field-to-Field: Transfer of infested soil to a new field on machinery or equipment
- During and Post-Harvest: Direct contact with infected tubers through bruises and wounds.
Favorable Conditions: High temperatures (75 to 82°F), very wet, poorly draining soils, moist storage conditions
Disease Cycle
Phytophthora erythroseptica spores (typically oospores) can overwinter in field soil, and in unharvested potato tubers (volunteers), as well as be transferred from other infested fields on machinery. Once present in a field, the pathogen can infect all underground parts of the plant through the epidermis. During very wet conditions, swimming spores (zoospores) can also move freely between plants, infecting through the epidermis, eyes, or lenticels. During and after harvest, infected tubers will rot and spread spores to healthy tubers through wounds and bruises, with high moisture in storage aiding infection. Spores left in a field can survive for up to seven years, and repeat the disease cycle in a following growing season whenever a susceptible crop is planted.
Cultural Control
Scouting regularly, especially in waterlogged parts of a field, allows for early identification of disease before significant spread and damage occurs. The following practices can also help prevent disease development:
- Destroy infested plant debris
- Rogue volunteer plants
- Maintain proper soil moisture
- Rotate away from susceptible crops (4 years)
- Avoid bruising and wounding during harvest
- Avoid harvesting in hot conditions
- Store tubers in cold, well-ventilated storage spaces
Chemical Control
Up-to-date Wisconsin-specific conventional in-furrow and postharvest fungicide information and recommendations can be found in the Commercial Vegetable Production in Wisconsin (A3422), a guide available through the UW Extension Learning Store website. It is important to be aware of the risk of pathogen resistance to the phenylamide fungicides (such as metalaxyl and mefenoxam). With use over time, these fungicides have selected for resistant pathogen populations in many locations. This means that the use of phenylamide fungicides will not control pink rot. Or, for home garden fungicide recommendations, see Home Vegetable Garden Fungicides (D0062), a fact sheet available through the UW Plant Disease Diagnostic Clinic website. Always follow label directions carefully.
References
- “Pink Rot / Potato / Agriculture: Pest Management Guidelines / UC Statewide IPM Program (UC
- IPM).” 2019. 2019. https://ipm.ucanr.edu/agriculture/potato/pink-rot/.
- “Potato Diseases: Pink Rot (E2993).” 2015. MSU Extension. 2015. https://www.canr.msu.edu/resources/potato_diseases_pink_rot_e2993.
- “Potato (Solanum Tuberosum)-Pink Rot.” 2015. Text. Pacific Northwest Pest Management
- September 11, 2015. https://pnwhandbooks.org/plantdisease/host-disease/potato-solanum-tuberosum-pink-rot.
Written by Amanda Gevens, Ariana Abbrescia, Russell Groves, and Ben Bradford. Last updated Nov 2023
