Heat Stress

Heat is very hard on grass (see our primer on grass growth for a discussion of heat, photosynthesis, and the growth cycle of northern turf grass). If you have brown areas in your lawn, and the temperatures have been in the mid to high eighties for a few days, the lawn may be damaged from heat. This is especially common in areas where grass doesn't get enough water (non-irrigated lawns, blocked sprinkler heads, not enough rain, etc.)

Look closely at the grass on the edge of the brown area. (Get on your hands and knees, it's OK. The neighbors will only laugh for a few minutes.) Examine the blades that are still green. Heat stress will be indicated by heat banding on the blades. Click the pictures below for examples of heat banding.

When submitted for review, I received the following comments:

"Doesn't look like a disease, looks more like heat stress (heat banding on the leaves) from a lack of soil moisture. Is it dry in these areas? [Fertilizer] burn would leave dark green margins on the patches and dollar spot would have a reddish margin on the lesions."

Zac Reicher
Professor/Turfgrass Extension Specialist
Dept. of Agronomy, Purdue University

It takes quite some time for grass to recover from heat damage. Keep the water on it and reseed if necessary.