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White Mold: How to Identify, Control, and Prevent Garden Fungus Diseases | The Old Farmer's Almanac

White Mold

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How to Identify and Control White Mold on your Plants and Vegetables

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Have you ever noticed dense white fuzz at the base of your plants—or, seen mold symptoms on stems, leaves, or blossoms? Learn about white mold, a fungal infection, and how to both prevent and control this plant disease.

What Is White Mold?

White mold, also known as sclerotinia, is a fungal disease that affects over 360 different plants in the garden, including beans, peas, lettuce, and members of the cabbage family. White mold on tomato plants is sometimes called timber rot. 

Mold symptoms appear on blossoms, stems, leaves, and pods that have water-soaked spots. Leaves will wilt, yellow, and die; pods may rot.

The host crops and plants are most susceptible during flowering, but young seedlings are also very vulnerable. White mold typically infects the plants early in the spring or summer and then develops unnoticed for a while. 

White mold fungus spreads spores in cool weather, which can infect other plants through the wind. This is why it is so important to catch white mold and destroy the infected plants quickly, to stop the spread of the fungal plant disease.

Identification

How to Identify White Mold Damage

White mold symptoms (signs of sclerotinia) tend to vary depending on the environment and type of plant, but here are some of the most common ones:

  • The stem might first appear to have a water-soaked part. At this point in the infection, the plant will look healthy from above.
  • Wilting of individual stems, especially at the base with tan discoloration.
  • Infected stems may appear to have tan to dark brown lesions on them. From these lesions, a dense, cotton-like growth will form under conditions of high humidity.
green beans affected with white mold
White mold takes over a bean plant with its dense cotton-like growth.
Photo Credit: The Ohio State University. 
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Control and Prevention

How to Control White Mold

  • 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.

Prevent White Mold

  • Be sure to use well-drained soil and space your plants properly to avoid crowding. Also, remember to avoid areas with poor air circulation.
  • When watering your plants, try not to water the tops of them. Or water the plants early in the day so they have the chance to dry before nightfall. Learn more about the best times to water your plants.
  • You can also spray your plants with an approved fungicide to help prevent infection. Spray the plants right before they bud, then spray again a week later.
  • Control your weeds. Weeds can host this disease and spread it to your plants.
  • If possible, remove all crop residue after harvesting. If residue is left, this disease may develop in it. White mold spores are long-lasting, so they will survive the winter if given the chance.
About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann

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