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Battling Fusarium Blight in Cool-Season Grasses

by Gabby Hyman, All About Lawns Columnist

Summer Patch fungus, also known as Fusarium Blight, can attack cool-season grasses used on residential lawns. It's particularly troublesome in Mid-Atlantic and Midwest regions, but can occur all over the country. It's not a pretty sight. The fungus appears as so-called "frog's-eye" spots on the lawn, starting in a reddish hue, then turning yellow. Untreated, it can kill off a Kentucky bluegrass lawn.

You'll most likely begin seeing traces of the fungus along the lawn fringes at driveways and sidewalks when outdoor temperatures begin climbing into the nineties. The fungus loves hot weather following explosive periods of heavy rains and high humidity, which is why lawns in the Midwest and central Atlantic states are prime candidates.
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While the fungus prefers Kentucky bluegrass, it can take hold on centipede grass, red and tall fescues, bentgrass, and perennial ryegrass.

Lawn Fungus Prevention and Treatment

The disease cycle for Summer Patch begins when the fungi recover from wintering in heavy thatch and begin to move upwards into the roots of the lawn. Once the temperatures in your region climb, the spores can kill off sections of lawn in as little as a week. Therefore, constant over-feeding your lawn with nitrogen fertilizers can increase thatch build-up and leave you vulnerable.

Once the fungus is apparent, you can treat it with varying degrees of success with fungicide, most typically with triadimefon and fenarimol. But the best treatment may be to over-seed bluegrass with a ryegrass mixture of a little over 20 percent. You should also de-thatch your lawn in the fall.

Compacted soil can also be part of the problem. Since the fungus gets its legs in dry weather, watering regularly through the season can sometimes help prevent breakouts. If your lawn has a history of Summer Patch fungus, you may have to reconsider using a grass type more suitable for your region and climate patterns, choosing a variety known for its resistance to fungus.

About the Author
Gabby Hyman has created online strategies and written content for Fortune 500 companies including eToys,, Siebel Systems, Microsoft Encarta, Avaya, and Nissan UK.

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