New York State IPM Program

The Heat’s On for Mums

If you’ve been warmer than you’d like of late, so have your mums. Pythium root rot likes it hot — and it likes mums, especially when their roots are stressed. Though this killer disease is widespread, it keeps a low profile when conditions don’t suit it — kicking into high gear when they do.

Symptoms: darkened roots; outer tissue slides right off; inner core stays white and firm. Nancy Pataky | Univ. Illinois

Say it’s hot … PLUS raining buckets … PLUS water is pooling on your growing pads … EQUALS … well, you do the math.

A whole slew of plant diseases share the “Pythium” family name, but what we’re looking at here is Pythium aphanidermatum. This water-mold fungus hides out on dirty flats and trowels or in potting media, or sneaks in on cuttings. Pythium root rot is hard to control once it’s gotten a hold, so prevention is the name of the game.

A too-hot, too-dry, too-wet routine stresses those roots; so does poor nutrition. Basic cultural controls like good sanitation and transplanting during cool morning or evening hours can help. And vigorous, well-nourished (but not over-fertilized) transplants are often more tolerant of rot.

If you’re struggling with recurrent pythium root rot, start with your classic cultural controls. But also consider a preventive drench or biological control agent, applied as early in the cropping cycle as possible. Remember to rotate drench materials — some populations of pythium are now resistant to certain commonly used fungicides.

Author: Mary M. Woodsen

Pests and pesticides — both can cause harm. How can we protect ourselves the least-toxic way? IPM is the sound, sensible, science-based approach that works wherever you do. The New York State Integrated Pest Management Program develops and offers tested tactics for pests new and old, whether on farms, offices, orchards, schools, parks, vineyards, more.... Wherever you find pests, you find IPM.

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