Pythium Root Rot
Pythium root rot
Common name
Pythium root rot
Water mold
Causal agent
It is caused by several parasitic oomycetes belonging to the genus Pythium. The pathogen attacks the plant in wet conditions.
Scientific name
Pythium aphanidermatum
Pythium debaryanum
Pythium ultimum
Symptoms & Signs
Pythium species usually attach root ends and young seedlings, leading to root rot. The roots turn black, and the infection may move to the bulbs turning them black and destroying them. The plant wilts and shows stunted growth.
Transmission
Pythium species are soil-borne; hence the disease spreads via the transfer of soil by fungus gnats, shore flies, or during contact. The spores travel to fresh soil and enter the plant below the ground. In addition, temperature conditions also favor the growth of pathogens. Pythium aphanidermatum prefers higher temperatures above 77°F (25°C), while Pythium ultimum attacks plants at lower temperatures below 68°F (20°C).
Time of concern
Throughout the growing season
Common hosts
Berberis
Calendula
Chrysanthemum
Delphinium
Dianthus
Gaillardia