University of Vermont Extension System
Department of Plant and Soil Science

Commercial Ornamental Horticulture (COH) Leaflet 39

Powdery Mildew on Phlox and Monarda

Leonard P. Perry, Extension Professor


The Problem


 Conditions affecting mildew

 Management Options

  1. Host resistance: select resistant cultivars (see below)
  2. Eradication: keep debris, dead leaves removed
  3. In greenhouses: decrease humidity through air flow, air exchange, proper watering
  4. In outdoor production: use proper spacing, fungicides (see below and references)
  5. In landscapes: thin stems and increase spacing for more air movement, water early in when leaves will dry quickly
  6. Begin scouting early in season (Memorial Day), begin application of sprays at onset of disease, continue through season if weather is conducive for disease

 Phlox Cultivar Resistance


Monarda Cultivar Resistance


Organic Controls Research (Vermont)

 Chemical Controls Research


Some Useful References