Lawn disease is usually caused by a fungus which grows from spores that are always present in lawn soil. The fungus is usually harmless, but when extreme weather conditions or faulty lawn care causes stress on the grass, the fungus can spread.
The fungal disease shows up as dead or dying lawn and usually strikes after extreme stress. Check for it after intense weather like drought, excessive rain or high humidity. Diagnoses are sometimes difficult, here’s a quick test. Pull up the infected lawn area. If the dead turf pulls away easily from the roots, it’s most likely that insects have eaten the roots. If the dead sod does not pull up easily it is probably a fungal lawn disease.
Proper care can usually prevent lawn disease, but sometimes our finicky weather can work against us. Water carefully, one or two heavy waterings a week rather than daily light ones. Aerate you lawn every 3 or 4 years, and overseed it with a new type of grass seed every 4 years or so to introduce new resistant varieties. Most important, be sure to mow your grass no shorter than 2 inches and don’t cut off more than a third at a time. Leave the lawn clippings on the grass.
Some common lawn fungal diseases include:
- Brown patch – Round brown areas. The grass will first look water logged and then brown and dry. To combat this lawn disease use slow release nitrogen fertilizer in the spring. Improve drainage and remove all infected grass clipping.
- Dollar spot – Light brown or tan spots the size of silver dollars. To get rid of this lawn disease feed your sod in the spring and fall. Apply light nitrogen frequently and be sure to remove and destroy infected grass clippings.
- Fusarium blight – red-brown rings with healthy grass in the center. This lawn disease is usually caused by drought. Water you lawn frequently and reseed with disease-resistant seeds.
- Powdery mildew – makes the grass blades look white or gray. The blades may turn yellow and wilt. This lawn disease likes to attack new grass. Correction of powdery mildew is to remove causes of excess shade, aerate your lawn and be sure not to over water or over fertilize.
- Pythium blight (Cottony blight) – makes the grass looks greasy in areas with the affected outer areas black with white or gray mildew. The treatment is aeration. Don’t over fertilize or over water the diseased area, and reduce nitrogen applications.
- Rust – The grass blades develop rust bubbles. Mow your lawn weekly and destroy all infected clippings. Be sure to feed, water and fertilize regularly.
- Red thread – looks like areas of pink grass. You can actually see red or rust colored threads on the grass. This lawn disease loves cool humid climates. Fertilize in spring and fall. Add lime as needed, improve drainage and remove all infected grass clippings.
- Snow Mold – white or pink spots on your lawn in spring. To prevent this lawn disease cut your grass short in fall and do not remove the clippings. Do not fertilize your lawn after mid-summer and improve your drainage.
- Stripe smut – blades appear to be striped. The treatment is aeration. Be sure not to over water the area and remove all infected thatch.
- Slime molds – patches of white, gray, or yellow slime. When the slime dries it looks gray, yellow or black. Aerate regularly and remove any thatch. Cut your grass to the lowest recommended height possible.