Powdery Mildew on Monarda
Monarda didyma, or beebalm, is an herbaceous square-stemmed perennial related to the mint family. Monarda plants prefer full sun or partial shade and rich, moist organic soil. They are highly susceptible to powdery mildew infection. Does this Spark an idea?
-
Features
-
The Erysiphe cichoracearum or Neoerysiphe galeopsidis fungus causes powdery mildew in monarda plants. The disease, which overwinters in infected buds and fallen leaves, releases spores during the spring that travel on the wind to infect new hosts. The fungus infects plants when temperatures are between 60 and 80 degrees F. Some fungal strains also prefer high humidity. Powdery mildew infections are most active in shady locations.
Effects
-
Powdery mildew infects both old and new foliage. A white powdery growth forms on the stems, leaves and flowers. Plants weaken and lose their vigor, and infected leaves turn yellow and fall prematurely, causing defoliation. The Oregon State University Extension indicates that some monarda cultivars such as Croftway Pink and Cambridge Scarlet are more susceptible than other varieties.
-
Prevention/Solution
-
The Oregon State University Extension recommends planting disease resistant monarda cultivars such as Jacob Kline or Marshall's Delight. Other resistant varieties include Colrain Red and Blaustrumph. Applying a preventative fungicide prevents new powdery mildew infections from developing. Monarda plants that grow in sunny areas are less susceptible than those grown in the shade. Spacing plants so that they have adequate air circulation and removing infected plant parts and leaf litter will also help to minimize outbreaks.
-
