BEEBALM               POWDERY MILDEW Powdery mildew is a common fungal disease on Monarda.

Symptoms: White to gray powdery growth on the leaf surface. (Pictured is a severe case.) Photo by Janna Beckerman.

General Information

Causal organism:	variety of fungi
Over wintering:	In plant material and debris
Months of infection:	Growing Season
Method of dispersal:	Wind
Infection point:	Leaves and buds (rarely)

Control Measures

Control:	Sanitation (rake all leaves in the fall) and properly water, fertilize, and mulch plants. Increase airflow and light penetration by thinning when possible to reduce humidity levels. Fungicides are not usually necessary.
Labelled fungicides: (First Application)	Sulfur or thiophanate-methyl (Cleary's 3336) (at first sign of infection)
Comments:	Powdery mildew is most severe in early spring and late fall, and when environmental conditions consist of warm days and cool nights. Several types of powdery mildew can overwinter in the buds.

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Plant Disease Diagnostics
University of Minnesota, Yard and Garden Clinic
Developed (1999) and maintained by
Chad J. Behrendt, Ph.D. and Crystal M. Floyd

For plant disease questions contact the Yard and Garden Line Content Last Updated 09/07/00 View University of Minnesota Disclaimer