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 Shirley,
There are a number of plant species with the common name of moon flower, but I am going to guess you have a Datura plant, in which case you may be looking at any one of the following viruses: Datura wilt virus, Datura distortion mosaic virus, Datura rugose leaf curl virus, or Datura quercina virus--all exhibit the wilting symptom. It is important to know if it is a virus and which one it is before treating it. I suggest taking some tissue cuttings (leaves and stem) and sending the sample to your local Cooperative Extension Office for testing. They will tell you a course of action to take.
It's hard to say for sure, but what you describe sounds like powdery mildew fungus, which won't kill the tree, but can be unsightly and might compromise the tree's long-term health, if allowed to spread. Go ahead and remove that branch, then monitor to see if the spores are spreading. There are a number of non-toxic products on the market for treating it, and even a few home remedies!
If you notice mold turn the soil over and bury the mold. Keep the soil as dry as possible and only water the individual plants not the entire garden. It also helps to add new fresh soil to the garden if the mold issue doesn't go away.
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If you are talking about potted plants, it could be a harmless (and common) fungus called saprophytic fungus. It usually results from a combination of over watering, poor drainage, and old or contaminated potting soil. If any or all of those conditions ring true, repot the plant with new soil (and possibly a pot that drains better) and water less frequently.