Greenhouse and Nursery - Pythium on Mums

Pythium is a common root rot of mums grown in pots and in the field. The following is a short article on the subject.

Pythium on mums is a soil-borne disease that thrives under prolonged periods of wetness and high soluble salts. It is known as a water mold. Plants that have experienced stress due to heat or drought are more susceptible to infection. Symptoms of root rot include chlorosis, wilting, and stunting. Roots infected with Pythium appear tan to black and water-soaked. The disease often will progress down rows and expand out from initial wet areas where it started.

Control: Cultural methods include removing infected plants, adjusting watering and fertilization practices, managing fungus gnats, and avoiding the reuse of pots and trays. Overwatering can lead to problems with this diseases. Mums in pots can also be grown off the grown on benches, inverted trays, blocks, or other means to avoid soil contact. Chemical control options include Subdue MAXX, Alliette, Truban, Alude, Terrazole.

Darkened roots from Pythium infection. Photo from Michigan State University Ornamental IPM.

Wilting mum due to pythium. Photo from University of Maryland Ornamental IPM program.

Some information taken from the University of Maryland Ornamental IPM Program newsletter - Greenhouse TPM/IPM Weekly Report, University of Maryland Cooperative Extension.