Powdery Mildew

Erysiphe graminis

For shaded lawns and landscaping, Powdery Mildew is a common lawn disease that primarily affects lawns in the northern United States from April through October.

Identify

Foliar

Foliar

The first sign of Powdery Mildew is a felt-like, white mycelium (lawn fungus) on the surface of grass leaves. The tufts enlarge and combine, causing the grass to appear grayish-white or powdery—hence the name. Grass severely infected by this lawn disease turns yellow, tan and eventually brown in color. In shaded areas, infected grass can thin and eventually die. Unlike other lawn diseases, Powdery Mildew does not require a film of water to start infecting your lawn. Typically, this grass disease is not severe enough to cause significant lawn problems—except in shady areas.

Life Cycle

A Powdery Mildew infection can occur only if all of the following conditions are present: 1. Pathogen: Erysiphe graminis lawn fungus 2. Host: Bentgrass, Bermudagrass, Fine Fescue, Kentucky Bluegrass or Ryegrass 3. Environment: Humid, cloudy climates with temperatures ranging from 60°–72°F in yards with low light and poor air circulation

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Control

Because you can't change your environment, the best way to control Powdery Mildew is to create conditions that will foster a healthy lawn. Not only will this make your yard unfavorable for Powdery Mildew growth, but it will also lower your risk of extensive damage should the lawn disease develop—plus you'll have the type of lawn you'll want to live on. For Powdery Mildew control and lawn fungus treatment, TruGreen® recommends the following cultural control tips: • Water 1 to 1 ½ inches per week to avoid drought stress • Water deeply one to three times a week rather than lightly every day • Avoid excessive amounts of nitrogen-based fertilizers to reduce lush leaf growth • Raise the lawn mowing height • Reduce the amount of shade • Increase air circulation

Diagram

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