Signs of Pythium root rot on poinsettias are wilting and stunting.
Pythium is a natural inhabitant of the soil and can survive there indefinitely as well as in debris in the greenhouse. Growers having re-occurring problems with Pythium , should review their overall production practices including fertilizing, watering and media handling. Over-watering and excessive fertilizer levels promote Pythium . Good sanitation is crucial for prevention. Keep hose ends off the floor and avoid contaminating growing medium by cleaning areas where plants are held, media is handled and plants are potted.
Suspicious plants can be diagnosed through your University diagnostic lab or through a private diagnostic lab.
Fact Sheets:
Root Diseases of Greenhouse Crops
Disinfecting the Greenhouse
New England Recommendation Guide (PDF) (scroll down for information on Pythium)