WSU Extension


Bean : Gray mold
(revision date: 6/2/2014)

Gray mold of green beans is a fungal disease. It can affect any aboveground portion of the plant. Initial infections often occur on old flowers which remain on the plant. After initial infection, gray mold can spread into the adjacent healthy tissues. Water-soaked lesions appear and quickly become covered with a gray-brown mass of fungus and spores. The disease is strongly favored by cool, moist conditions and can survive on infected plant debris.
Management Options

Non-Chemical Management
  • Rotate crops. Do not plant beans in the same location each year.
  • Remove plant debris from the garden. Destroy or discard (do not compost) diseased materials.
  • Space plantings to provide good air circulation and reduce humidity.
  • Avoid overhead watering, especially during and after the bloom period.
  • Irrigate only in the morning, so plants can dry during the day.
Select non-chemical management options as your first choice!

Chemical Management

Begin application during early bloom stage or when disease first threatens. Repeat at weekly intervals or as necessary.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Fung-onil Multi-Purpose Fungicide Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 60063-9-4
  • GardenTech Daconil Fungicide Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 67572-82-71004
  • Ortho Max Garden Disease Control Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 239-2522
  • This list may not include all products registered for this use.
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Caption: Botrytis gray mold on bean pods
Photo by: R.S. Byther