Pythium species cause damping-off, root rot, crown and stem rot of all plant species. Pythium is favored by high fertility and high moisture; avoid over-watering and over-fertilizing. Pythium is a natural inhabitant of the soil and can survive there indefinitely as well as in dirt and debris in the greenhouse. Use soilless growing media. Keep hose ends off the floor and avoid contaminating growth medium with soiled hands, tools, or flats. Fungus gnats and shore flies can introduce and spread plant pathogenic fungi into a crop. Biological and chemical methods are available for controlling these insects. Fungicides for controlling Pythium include Aliette, Alude, Banol, Banrot 40 WP, ProPhyt, Subdue Maxx, Terrazole 35 WP, and Truban 30 WP. Many greenhouse isolates of Pythium are resistant to Subdue. Rotate fungicide applications among active ingredient groups (FRAC code) to avoid resistance development in the pathogen population.
Fact Sheet: Root Diseases of Ornamental Crops