HOW TO PREVENT PYTHIUM SEED AND TUBER ROT
Pythium fungus is found in almost all cultivated soils and is responsible for seedling diseases in many crops. Potato seed and tubers become infected in the field through wounds that may or may not be visible. Wet, warm soils are necessary for infection.
Late planted, cut potato seed is very vulnerable to infection. Potatoes harvested when temperatures are above normal for the season are very susceptible, especially if the soil is moist.
Soil with large populations of pythium and other organisms suppress both the saprophytic and pathogenic activity of Pythium species.
The addition of organic matter may contribute to soil microbial populations.
Minimizing periods of excessive soil moisture are essential for controlling Pythium diseases.
Improve the drainage of the seed raising beds by planting on raised beds and if symptoms are present only irrigate for short periods on alternate plant beds to maintain plant growth.
Take precautions for seed rot against Pythium
Only whole seed should be used for late plantings.
- To exclude wounds handle seed gently.
- Treat seed with a recommended fungicide. Presently available seed treatments are not completely effective against the leak fungus. However, they protect seed against other seed rotting fungi and thus protect against subsequent invasion by the leak fungus.
- Plant deep; cover shallow. Get the young plant up as quickly as possible. A seedling under stress is more susceptible to seedling and seed rot disease.
Take precautions for tuber rot against Pythium
Try to minimize mechanical injury at harvest.
Do not harvest when temperatures are above normal and soil is moist.
Do not expose harvested potatoes to stand in the sun.
Heal-in tubers: temperature 50 to 600 F and relative humidity 85 to 90 percent for
7 to 14 days.
If pythium develops in storage
- If potatoes are destined for processing, do not lower temperature.
- Force dry, warm air through the pile and exhaust moist air.
- Do not regrade. Regrading opens new wounds which are susceptible to ever present bacterial rots.
- If potatoes are for table stock, drop temperature to 400 F or lower.
