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Summer Patch

by Don Janssen, UNL Extension Educator

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Summer patch has been showing up on lawns for the last 2-3 weeks. This disease is one of the most damaging problems of turfgrasses and sometimes one of the most frustrating to control. The main host plants are Kentucky bluegrass and fine-leaved fescues, which are often found in "shade-adapted" grass seed mixes.

Summer patch is caused by a fungus which lives in the soil and attacks the roots. It produces dark-colored hyphae (fungal strands) that can damage and kill roots. The symptoms of summer patch are striking: circles or semicircles of grass, 6 to 12 inches in diameter, that are light tan in color and matted in appearance. Tan circles with green grass in the center are often referred to as "frog-eye" symptoms because of the dark center and light border. Symptoms can proliferate in a lawn to the point where some areas have more damage than healthy lawn. A similar disease, called necrotic ring spot, produces identical symptoms in fall and spring, but summer patch typically appears in July and August. Experience indicates that summer patch is by far the more common problem.

Management of summer patch starts with good cultural practices. This means raising the mowing height to at least 3 inches in summer. If thatch is a problem, it will be helpful to vertical-mulch or power-rake the lawn in spring and fall (appropriate equipment can be rented, or you can contract to have this done twice a year). Core-aerating helps relieve compaction and helps roots obtain oxygen in heavy soils (again, you can rent equipment or hire a specialist).

A complementary approach is application of fungicides. Systemic fungicides labeled for summer patch control can be applied every 3-4 weeks beginning when the grass starts to grow (early May) and continuing through the end of June.

When summer patch is severe, overseeding is probably the only option. It's important to overseed with blends and mixtures of grasses with tolerance or resistance to summer patch. Check with lawncare services or garden centers for appropriate blends that work. A blend of Kentucky bluegrasses with turf-type tall fescue varieties will lessen the risk of severe summer patch and also reduce the risk of other diseases. This is a long-term strategy that can help the lawn avoid severe summer patch die-off in the future.

(This resource was added August 2007 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement)

University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office

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University of Nebraska-Lincoln
in Lancaster County
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Lincoln, NE 68528
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