This year garden mum growers in southern New England found the cool, wet weather during June and July created challenges to producing healthy plants. The weather delayed plant development, which forced some growers to push their mums with fertilizer trying to keep the plants in a vegetative state. Univ. of Mass. Extension personnel report some of these growers began to encounter problems with Pythium stalk rot in late August. The pathogen, most likely Pythium aphanidermatum, was observed on the roots and stems. Symptoms of Pythium infection vary with temperature, moisture and the Pythium species involved. Since Pythium is favored by high fertility and high moisture, avoid overwatering and overfertilizing. The pathogen is a natural inhabitant of soil and can survive there indefinitely, as well as in soil and debris in the greenhouse. Use soilless growing media. Keep hose ends off the floor and avoid contaminating growing medium with soiled hands, tools or containers. Pythium-controlling fungicides include Aliette, Alude, Banol, Banrot 40 WP, Subdue Maxx, Stature DM (drench) Terrazole 35 WP and Truban 30 WP.
*Photo by Paul Lopes, UMass Extension