Caption
Cottony white growth on a plant stem caused by the pathogenic fungus Sclerotinia sclerotiorum, which leads to the disease known as white mold.
Have you spotted a soft, white fuzz creeping up your plants or vegetables—almost like cotton candy on the stems? That’s white mold, or Sclerotinia, a stubborn fungus that thrives in cool, damp gardens. It can infect beans, tomatoes, lettuce, peas, and dozens of other crops, often appearing right when plants are blooming. I’ve learned over the years that catching this disease early is key, because once it spreads, it’s hard to stop. Here’s how to identify, control, and prevent white mold before it takes over your garden beds.
What Is White Mold (Sclerotinia)?
White mold, or Sclerotinia sclerotiorum, is a fungal disease that affects more than 360 types of plants, including beans, peas, lettuce, tomatoes, cabbage, and many flowering ornamentals. When white mold hits tomato plants, it may be called timber rot.
This fungus thrives in cool, damp conditions, usually during spring or early summer. Spores spread through the air or by water splash, infecting flowers and stems when humidity is high and air circulation is poor.
NOTE: White mold is not the same as white rot (Sclerotium cepivorum), which primarily attacks onions, garlic, and related crops. White mold spores persist in the soil. White rot spores survive mainly in onion and garlic bulbs or in infested soil.
How White Mold Spreads
White mold spores can travel by wind, water, tools, or even your hands after handling infected plants. They thrive in humid, cool conditions, often during flowering or early growth stages. The spores land on plant tissue—especially flowers—and germinate in cool, moist environments. Once this fungus takes hold, it can overwinter in soil for several years. That’s why prevention is key: once it’s in the soil, it’s tough to eliminate.
Identification
How to Identify White Mold on Plants
White mold symptoms vary by plant, but the early warning signs are often subtle. Keep an eye out for:
- Fluffy, cottony white fungal growth on stems, blossoms, or pods.
- Water-soaked spots on stems or leaves
- Wilting or yellowing leaves, starting at the base
- Black, seed-like sclerotia that form later inside stems or pods
- Leaves or pods may rot, and stems can become brittle
Tip: The white growth appears first, then black sclerotia form later. This differs from white rot, which usually affects the bases of bulbs like onions and garlic. If you notice one plant showing these symptoms, it’s best to act fast—white mold spreads easily to nearby plants.
Comments
Hi, P.J.: Excellent question! From a technical standpoint, the answer is yes. Assuming that you mean a leafy veggie, and not something that you would peel or de-pod anyway, it is indeed possible to wash them thoroughly enough to eat (say, with a very weak bleach solution, then assiduous rinsings), especially since some might end up being boiled anyway. From a practical and 100% safety standpoint, though, we wouldn't do it.
Hi, Lea: Meet powdery mildew. Before doing anything drastic, just try washing it off with a water spray. (Some folks say plus milk, and/or plus baking soda, etc.; we say keep it simple, at least to start.) Do it in the morning so that the leaves have time to dry out before the humid part of the day, humidity being the main culprit, not water itself.
It sounds as if you may be watering too frequently. Make sure that you aren't saturating the soil; let it dry out and then deeply water and then let it dry out again between waterings. Take the seedlings off any watering trays so they're not wet on the bottom; let them drain and put on a cloth. You can scrape off the white mold; if it gets too bad, you might need to replant the seedlings in clean soil. You could also consider an anti-fungal product; ask your garden center. Finally, some readers suggest adding a little sand and others say sprinkling with cinnamon helps!
To prevent white mold, avoid wet soil or overwatering. Just keep soil moist.
Use raised beds.
Create furrows in the soil for watering or irrigation so that the water doesn't just flow all over the bed surfaces.
Do not water from overhead and get the plants wet; water at the soil line.
Space plants extra far apart to allow good air circulation.
Remove and destroy entire infected plants and crop residues as soon as you see any signs of mold.
Hope this helps.
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Hi Branden,
We suggest that you remove the plant from the pot. Discard any soil that has mold on it and replant in a new bigger pot with light potting soil for containers.