Fungi in My Grass Lawn

Avoid applying excessive fertilizer to the yard in the spring to prevent fungal diseases.

Fungi or fungal diseases commonly infest lawns, especially if there are underlining problems. Excessive thatch buildup, overwatering and improper fertilizer applications can encourage lawn fungal diseases. Gardeners should monitor their lawns in the spring to diagnose fungi problems and treat lawn areas. Lawns that go untreated can eventually die out from diseases.

Necrotic Ring Spot

Necrotic ring spot is cause by Leptosphaeria korrae fungal spores. This fungal disease is at its most active in the spring and fall months, according to North Dakota State University Extension. Symptoms begin as discolored, irregular patches that are 6 to 24 inches in diameter. Patches can be from straw-colored to bright-red grass blades. Stress from the disease may kill off grass blades, especially when your lawn experiences hot temperatures or drought. Treat necrotic ring spot with fungicide to kill off the fungi spores.

Rhizoctonia Yellow Patch

Rhizoctonia yellow patch is caused by Rhizoctonia cerealis, which germinates and spreads during cool moist weather. Newly laid sod, thick thatch laying between the grass and soil, and soil compaction raise the risk of the grass contracting rhizoctonia yellow patch. As the disease progresses, grass blades will yellow, sink into the soil and take on a reddish tint. Because no fungicide is available to treat the disease, gardeners should reseed dead areas. Furthermore, reduce your irrigation to protect your grass from the disease.

Leaf Spot

Leaf spot is caused by Bipolaris sorokiniana fungal spores. The disease reproduces in warm weather and turns grass blades purplish red with tan centers. Left untreated, grass blades die out and the entire blade is in danger of dying off. With dead grass-blade centers, the grass is vulnerable to contracting another fungal disease called melting out, which is caused by Drechslera poae fungal spores. Fungicide should be applied to the lawn as soon as the first signs of leaf spot are noticed, to prevent large areas of dead grass.

Powdery Mildew

Erysiphe graminis fungal spores cause powdery mildew disease. A white powdery substance on the lawn is one of the best indicators that you lawn has contracted the disease. Gardeners may see a raise in powdery mildew damage when temperatures are between 60 to 72 degrees Fahrenheit, according to North Dakota State University Extension. Dig up dead grass and reseed in those areas. If you yard has overhanging trees casting too much shade, prune back branches to increase the sunlight in the yard.

References

• North Dakota State University and U.S. Department of Agriculture; Lawn Diseases; H. Arthur Lamey, Cynthia L. Ash, Ward C. Stienstra, July 1996
• University of Rhode Island: Some Common Fungal Diseases of Turf