"Damping-Off" (Pythium or Rhizoctonia)
in the Low Desert

HOST: Seedlings of many plants including most vegetables and flowers.

SYMPTOMS:

• Seeds may fail to emerge, when inspected are soft, dark and disintegrating.
• Seedlings are attacked at or below the soil line; infected tissue is water-soaked and discolored. The stem becomes too weak to support the rest of the plant, and it falls over. It quickly withers and dies.
• Damage occurs in a circular pattern

CAUSE:

Either the fungus Pythium or Rhizoctonia. Plants are most vulnerable when the soil is kept too wet and/or the same varieties are planted repeatedly in the same beds.

MANAGEMENT:

Prevention is the key as once symptoms are apparent the plant quickly dies. Control the planting environment: high soil moisture, low soil temperature, and high humidity are a deadly combination.
• Use sterile potting media.
• Keep benches, pots, garden tools, and hoses clean. Fungus spreads readily via garden tools.
• Select planting date to promote fast germination, wait for soils to warm prior to planting spring crops.
• Use seeds that have been pre-treated with a fungicide.
• Good aeration and soil drainage are important: don't overcrowd, allow air to circulate between plants.
• Avoid over watering or over fertilizing.
• Rotate plantings.
• Soil drench with a fungicide.

To Gardening and Landscaping in Maricopa County, AZ