Scientific Name
- Phoma exigua var. exigua
Identification
- Tubers become infected through wounds caused by rough handling during harvest and grading operations, leading to the development of the disease in storage.
- External lesions are circular, slightly sunken, greyish-brown, and the size of a thumbprint. The tissue underneath the lesions is black, shrunken, and decayed, with cracks often forming on the surface of the lesions.
- The black, rotten tissue can be easily scooped out from the surrounding healthy tissue.
Often Confused With
- Fusarium dry rot
Biology
- The fungus persists either in the soil or on infected seed tubers.
- Infection occurs through wounds or bruises at harvest or when grading. Disease incidence is higher when the soils are wet and cool at harvest.
Period of Activity
- Infection occurs at harvest, and the disease develops in storage.
Scouting Notes
- There are no above-ground symptoms.
Thresholds
- No established thresholds.
Management Notes
- Use healthy, certified seed.
- Minimize tuber wounding and/or bruising at harvest and during potato grading operations.
