Rhizophus soft rot: Rhizopus stolonifer Symptom s Infection and decay commonly occur at one or both ends of the root, although infection occasionally begins elsewhere. Rotting may be inhibited under dry conditions, but under humid conditions the affected sweet potatoes become soft and watery, and the entire root rots within a few days. If the humidity is high, the sweet potatoes become heavily "whiskered" with a grayish black fungal growth. This feature distinguishes Rhizopus soft rot from other storage rots. The color of the root is not significantly altered, but an odor is produced that attracts fruit flies to the area. Infection is especially likely if the relative humidity is between 75 and 85 percent during storage or transport. Also, the longer roots are stored, the more susceptible they become. Chilling and heat damage also predispose sweet potatoes to infection. Soft rot is very destructive when sweet potatoes are washed, packed, or shipped to market during cold weather. Management Carefully handle sweet potatoes during harvest to prevent unnecessary wounding. This is the most important control method for soft rot. Properly cure roots immediately after harvest. Store roots at 55 to 60 degrees F. Avoid handling stored roots because handling can create new wounds. Recuring is one possible solution to this problem. Apply a recommended fungicide after harvest. Do not allow sweet potatoes to be exposed to sunlight for extended periods (to prevent heat damage) or to be chilled in the field.
Infection and decay commonly occur at one or both ends of the root, although infection occasionally begins elsewhere.
Rotting may be inhibited under dry conditions, but under humid conditions the affected sweet potatoes become soft and watery, and the entire root rots within a few days.
If the humidity is high, the sweet potatoes become heavily "whiskered" with a grayish black fungal growth. This feature distinguishes Rhizopus soft rot from other storage rots.
The color of the root is not significantly altered, but an odor is produced that attracts fruit flies to the area.
Infection is especially likely if the relative humidity is between 75 and 85 percent during storage or transport. Also, the longer roots are stored, the more susceptible they become.
Chilling and heat damage also predispose sweet potatoes to infection. Soft rot is very destructive when sweet potatoes are washed, packed, or shipped to market during cold weather.
Carefully handle sweet potatoes during harvest to prevent unnecessary wounding. This is the most important control method for soft rot.
Properly cure roots immediately after harvest.
Store roots at 55 to 60 degrees F.
Avoid handling stored roots because handling can create new wounds. Recuring is one possible solution to this problem.
Apply a recommended fungicide after harvest.
Do not allow sweet potatoes to be exposed to sunlight for extended periods (to prevent heat damage) or to be chilled in the field.
