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White Mold on Plants: Identify, Prevent, and Treat Sclerotinia Fungus

White cottony mycelium of Sclerotinia sclerotiorum on plant stem causing white mold disease.

Cottony white growth on a plant stem caused by the pathogenic fungus Sclerotinia sclerotiorum, which leads to the disease known as white mold.

Image Credit:
RJymm/Wikimedia
Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

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.

white mold growth on a cabbage stem
White mold creeping up a cabbage stem—once it starts, this fungus can spread fast in damp garden beds. Credit: Cornell

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.

Sclerotium cepivorum (white rot) on onion bulb
White rot on an onion bulb. This disease only affects allium species, especially onion and garlic. Credit: Steven Koike

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
Early white mold (Sclerotinia) infection showing cottony white mycelium on snap bean stems.
White mold on snap beans shows the fluffy, cotton-like mycelium of the fungus on stems and pods. This white growth is the first visible sign of the disease. Credit: Ohio State University

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.

Black sclerotia forming in white mold growth on snap bean stems.
See the black spots that look like mouse droppings on the white mold? As white mold matures, black, seed-like sclerotia form, allowing the fungus to survive in soil for years. Credit: Cornell University

Control and Prevention

How to Control and Treat White Mold

If you find infected plants, here’s what to do:

  1. As soon as you notice any diseased plants, destroy them immediately—do not compost them.
  2. If your soil is infected, remove as much of it as you can and replace it with clean soil or solarize it (cover the infected ground with clear plastic for several weeks in full sun) to prevent the spread of the disease.
  3. Avoid overhead watering—water at the soil level instead.
  4. Consider using an organic fungicide labeled for white mold (apply before flowering and repeat one week later).
  5. Rotate crops so the same type of plant isn’t grown in the same spot each year.

How to Prevent White Mold in Your Garden

An ounce of prevention really is worth a pound of cure when it comes to fungal diseases. Here’s how to keep white mold away:

  • Space plants properly for good air circulation.
  • Water early in the day so foliage dries before nightfall. Here are the best times to water your plants.
  • Keep weeds in check—they can harbor the disease.
  • Clean up all crop debris after harvest. The fungus can survive on leftover stems and leaves.
  • Mulch or use plastic barriers to reduce soil splash onto plants.
  • Rotate crops yearly, especially legumes, cabbages, and lettuce.

If you’ve struggled with white mold in the past, try planting resistant varieties or adjusting garden layout for better airflow.

White Mold on Houseplants

White mold can appear on houseplant soil or leaves if conditions are too damp. To fix it:

  • Let the top inch of soil dry out between waterings.
  • Remove any white fuzz with a paper towel and discard it.
  • Improve air circulation indoors.
  • Repot with fresh soil if needed.

White Mold vs. White Rot and Other Diseases

It’s easy to confuse white mold with white rot. Here are the key differences.

FeatureWhite Mold (Sclerotinia)White Rot (Sclerotium)
HostsBeans, peas, lettuce, cabbage, tomatoesOnions, garlic, leeks, shallots
SymptomsCottony white growth on stems/flowers; black sclerotia in pods/stemsWhite fuzzy growth at base of bulbs; bulbs rot; black sclerotia in/on bulbs
SpreadAirborne spores, soil, water splashSoilborne only; spreads via bulbs or infested soil
SeasonCool, humid spring/early summerCool, wet soil conditions; onion/garlic beds

Some gardeners can also confuse white mold with gray mold (Botrytis) or powdery mildew.

FAQ About White Mold

Q: What causes white mold?

White mold thrives in cool, damp, and poorly ventilated conditions—especially when plants are crowded or watered from above. The spores can persist in soil for several years and infect plants when moisture levels are high.

Q: How do I get rid of white mold?

Remove infected plants, solarize the soil (cover it with clear plastic for several weeks in summer), and rotate crops yearly.

Q: How is it different than white rot?

White mold attacks many vegetables; white rot attacks onions/garlic. The two diseases look similar but affect different plant families.

Q: Can white mold spread to my houseplants?

Yes, if the soil stays damp. If you see white fuzz, scrape it off, let the soil dry out, and improve air circulation. Repot with fresh soil if needed.

Q: Can I eat infected vegetables?

No, discard them. The fungus can produce toxins.

White mold can be discouraging, but with good garden hygiene, smart watering, and crop rotation, it’s possible to keep it at bay. I always remind new gardeners: even the best of us lose a plant or two to fungus—it’s part of learning how to work with nature, not against it. Keep observing your garden, and before long you’ll spot trouble before it spreads!

Plant Disease

About The Author

Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

Catherine Boeckmann is the Executive Digital Editor of Almanac.com, the digital home of The Old Farmer’s Almanac. She leads digital editorial strategy and publishing across a wide range of Almanac sub...

Read more from Catherine Boeckmann

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Comments

<span>Barbara Moody</span> Sun, 05/12/2019 - 21:46
I planted my first 8 x 2 raised garden. I put boards on each corner, with wire fence all around, nice. I put tomato's on one end & squash, bell peppers & cucumber on the other. I covered the entire garden with sheets for more than a week, to prevent severe thunderstorms from destroying my plants. I took the sheets off today to find white mold under the first two tomoto plants, on the soil only & not on the plants. I scooped out all the mold from the soil. I was so excited to have vegetables starting to grow on all plants. Am I screwed after all my work, cost & excitement or can my garden be salvaged from this mold. Please please advise me what to do?? Thank you.
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 05/13/2019 - 16:11

As long as the garden receives proper air circulation and is allowed to dry out between waterings, the white mold should be kept at bay. Consider placing landscaping fabric over the soil around the plants to prevent mold (and other diseases) from splashing up onto the plants from rain.

 <span>Tcbelle</span> Thu, 06/27/2019 - 15:54
I have white sections outside in raised bed that is not yet even planted. Paid a good price for that dirt and don't know why it is showing up. Also have one bed planted with lettuce and beets that has a greenish coating over top of dirt. What's going wrong? Please help me.
<span>Donna Suhre</span> Tue, 07/03/2018 - 19:06
There is a white fungus growing on the soil in our raised vegetable garden. We used chicken manure as fertilizer in the spring. The plants are growing great, but is it safe to eat the vegetables?
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 04/26/2018 - 16:15

No, it's not recommended. See here, and read above:

  • As soon as you notice any diseased plants, destroy them immediately.
  • If your soil is infected, remove as much of it as you can and replace it with clean soil.
  • You can use a barrier, such as plastic or mulch, to cover the infected ground to prevent the spread of the disease.
 <span>Amanda Beggs</span> Mon, 06/26/2017 - 15:04
i got a like a cotton white fugus on my roses what do i need to get rid of it
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 06/27/2017 - 14:59

It sounds like your roses may have powdery mildew. If possible, remove the infected leaves and treat the rest of the plant with a fungicide, which you can find in your local hardware store, garden center, or online. Powdery mildew forms when conditions are warm and humid, so if you happen to be watering your roses from overhead, try watering at the base of the plant instead to reduce moisture around the leaves.

 <span>Becky Tippen</span> Sun, 04/16/2017 - 18:10
I purchased a Sour Sop tree about 2 months ago, shortly after buying the tree the leaves started to get brown spots. I removed the leaves and it looked like the tree was doing ok now some leaves are spotting again. I did not have food for it so I used raised bed food for vegetables which ended up molding. I replaced the food with citrus tree food as well as a thin layer of cedar chips to keep the bugs off and again it molded. I did have a raised bed garden and was using compost tea to water the plants. Out of about 30 plants I have 3 left. The soil did mold is that because of the compost tea? I also have a mite problem which may have aided in the plants dying, I had them inside a lot of the winter which is where the mites are.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 04/18/2017 - 17:18

Have you contacted the source from which you purchased the plant? It may have been diseased or at least your vendor may have been able to provide some guidance. These are tropical plants that are vulnerable to a number of pests. That said, it is not a plant with which we have any experience, and would advise you to read up on it here: https://hort.purdue.edu/newcrop/morton/soursop.html (Perdue is an excellent resource). We would also suggest that you contact the cooperative extension nearest you (chick on your state here: http://www.almanac.com/content/cooperative-extension-services ) If the folks at the extension do not have an answer they may very well refer you to a colleague at a service that is knowledgeable.

 <span>Earl W. Krause</span> Wed, 10/19/2016 - 15:07
Barnstable Co. Ext. Serv. gave me a bad diagnosis, since your article does not seem to correspond to my situation. The "white mold" I have is NOT on the plants, but on the soil surface. There is nothing growing on plants, but I was worried about it's effect on my plants. It is ONLY on clear soil. It fades to gray color and disappears, but returns with moisture. It's spotty, in many areas, but only on clear soil. It's like fuzzy white ground cover. Can you give me some better advice?