Last Updated August 19, 2004
Maricopa County Cooperative Extension Home Horticulture:
Gardening & Landscaping in the Low Desert
"Damping-Off" (Pythium or Rhizoctonia)
in the Low Desert
HOST: Seedlings of many plants including
most vegetables and flowers.
- 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
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.
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
"Damping-Off" (Pythium or Rhizoctonia) in the Low Desert
visitors since June 9, 1998
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, Maricopa County
© 1997 The University of Arizona, College
of Agriculture, Cooperative Extension,
County. Comments to Maricopa-Hort@cals.arizona.edu
4341 E. Broadway Road, Phoenix, AZ 85040, (602) 470-8086 ext. 323