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Lawn Disease - Powdery Mildew

Common on Kentucky bluegrass growing in the shade


Lawn Disease - Powdery Mildew
photo © Clemson University - USDA Cooperative Extension

What is powdery mildew?

Powdery mildew is a fungal disease common to many plants each with it's own species of the disease. Powdery mildew on lawns is most common on cool season grasses, Kentucky bluegrass specifically.

Powdery mildew can appear quickly on a lawn, mainly in shady areas and more frequently during cloudy or overcast periods.The presence of powdery mildew is evident by a white dust appearance on the leaf blades.

The affected leaves may yellow and die over time, but generally the plant will survive with powdery mildew present.

How is powdery mildew controlled?

Powdery mildew is best controlled by reducing the amount of shade that the grass is in by pruning or thinning trees for increased sunlight and air circulation.

Shade tolerant grass species and improved cultivars are also available which are able to withstand extended periods with reduced sunlight.

It is also wise to avoid excessive nitrogen levels, overwatering, and close mowing lawns with powdery mildew, as these factors can increase plant stress and weaken or kill the grass.

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