Gray Mold: How to Identify, Control, and Prevent Botrytis | The Old Farmer's Almanac

Gray Mold or Botrytis


Gray mold has compromised these Riesling grapes.

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Photo by Rob & Lisa Meehan, Wikimedia Commons
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How to Identify and Control Gray Mold Fungus or Botrytis

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Here are tips for how to identify, control, and prevent gray mold, or botrytis.

What is Gray Mold?

Gray mold is a fungus otherwise known as Botrytis cinerea that can affect any part of a plant and is one of the most common diseases found among bedding plants. This disease will easily infect plants that are already damaged or beginning to die. It then spreads quickly and can cause extensive damage to healthy parts of plants.

Moisture is one of the main causes of gray mold. The wetter your plants are, the more susceptible they are to becoming infected. Your plants also must be injured before they can become infected. Be careful around your plants to prevent this.


How to Identify Gray Mold Damage

  • The symptoms of gray mold depend on the type of plant and environmental conditions, but generally spots that appear water-soaked will form on the leaves. These might appear white at first.
  • These spots will then change color from gray to brown, eventually covering most of the leaf and causing it to wilt. The brown coloration is what often causes people to confuse gray mold with brown mold.
  • Under really humid conditions, grayish webbing may appear on the leaves. In this webbing are structures that contain fuzzy spores. Spores become active and are released with any activity at all.
  • Petals, stems, and buds can also be infected.
  • Eventually, all of the infected parts of the plant will be covered by a fuzzy gray growth, causing you to seemingly have gray flowers.


Photo Credit: Francesca Peduto Hand, The Ohio State University. The fuzzy gray spores characteristic of botrytis infect an impatiens plant.

Control and Prevention

How to Control Gray Mold

  • Remove the infected plants and destroy them.
  • Clean thoroughly between your plants so that the disease cannot infect your other plants.
  • You can try using sprays with cultural controls on your plants to prevent further infections.

Prevent Gray Mold

  • Handle your plants carefully when transplanting and pruning. Gray mold usually attacks wounded plants, so avoid harming your plants.
  • Keep your plants dry. Avoid overhead watering and watering late in the day. Give your plants time to dry off after watering them during the day.
  • Space your plants properly to encourage good air circulation.
  • Remember to clean between your plants. Remove any debris, including cuttings and dead leaves.