What is it?
A distinctive fungal disease that is fairly easy to identify by its white powdery residue on leaves and stems. Powdery mildew thrives in high humidity and although it’s generally not fatal to a plant, it can spread up and down the length of the plant and decrease blooms/yield.
How to Diagnose the Problem
Look for powdery splotches of white or gray on the leaves or stems of a plant. Damage can appear on the top and bottom of a leaf. Posdery mildew is active between May and September when humidity is high. Many plants can show signs of powdery mildew: bee balm, cosmos, crabapples, hydrangea, lilacs, oaks, pansies, phlox, roses, sweet peas, verbena and many more.