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There are several reasons lawns turn brown during the summer, and investigation is needed to pinpoint what may be causing problems. The most common culprit is drought stress. Common turf grasses go dormant during hot, dry weather as a protective measure when they do not receive sufficient moisture. When provided adequate water, they remain green but growth slows.
A few simple steps can be taken to determine drought stress. Try pushing a screwdriver into the soil in several parts of the brown area. If it is difficult to insert compared to green areas, this usually indicates drought stress. If grass is growing in rocky soil, it may be necessary to dig a small hole to determine soil moisture.
Another indicator of drought stress is brown spots that appear in rough patterns. Grass may remain green in circular patterns around sprinklers while surrounding grass is brown. Additionally, turf in shaded areas may remain green, while in hotter areas it goes dormant. When grass goes completely brown from a lack of water, it can take 3-4 weeks of sufficient irrigation for green grass to appear. Irrigating above normal water requirements does not revive the lawn more quickly.
To avoid lawn areas going completely dormant, watch for early signs of drought stress. They include turf turning a slightly blue or gray color and footprints remain on the lawn after it has been walked on. Do not increase irrigation time of the entire sprinkling system in an attempt to alleviate a few brown spots - it's better to spot-water with a hose sprinkler or be tolerant of a few brown spots. They usually go away when cool weather returns.
Another major reason lawns turn brown is lawn-feeding insects. To determine if you have this problem, pulling on brown areas of the lawn is useful. If turf is easily removed with few to no roots, insects may be the cause. In some instances, the lawn pulls up almost like a rug. Common lawn-feeding insects include various species of white grubs, billbugs and sod webworm. Specific information on these insects can be found in the related links of this article.
These pests seem to be more common in overly maintained lawns. Over maintenance includes applying too much water and fertilizer and mowing excessively short. When extensive damage occurs, several weeks to months are required for the lawn to recover once insects are controlled. Conversely, maintaining a healthy lawn is an effective tool in controlling insect problems. A useful factsheet on lawn maintenance can be found in the related links section. When needed, preventative insect treatments can be applied in the spring. An additional midsummer application may be required, depending on the pest.
Lastly, if brown grass is sufficiently watered and does not pull up easily, it may be a fungal disease. At this point, it is useful to submit a sample to the USU Extension Pest Lab for further diagnostics, and local extension offices may also be helpful. They only charge $7. Local Extension offices may also be helpful.
