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Summer Lawn Diseases: What to Look For

Summer Lawn Diseases: What to Look For

While the springtime is all about preparing your lawn for the showcase summer months, the maintenance and care throughout the summer can make all the difference in keeping it healthy. Summer in particular is the time of year when lawns are more susceptible to a variety of lawn diseases. The high humidity paired with heavy rains (such as the ones we have experienced over the past month in Wisconsin) are the perfect breeding ground for many types of fungi that can wreak lasting damage if not properly identified and treated promptly.

Preventing lawn diseases is always easier than treating once they emerge, and the groundwork is laid in the spring. However, diseases are common with nearly all grass types. While following best practices may hinder the development of diseases, perfect hot, humid, and wet conditions can easily activate the microscopic living organisms at the root of the problem. When your lawn shows signs of disease, it is vital to strike and treat while it is in the early stages, as untreated fungi can spread quickly. Your lush green lawn may soon be marred with bare patches and brown spots.

Pathogenic fungi are the cause of most lawn diseases and they are usually present in your soil. These fungi may remain dormant until environmental conditions are right for an outbreak. If the conditions are right, the pathogen is present in your soil, and your type of grass is susceptible, the fungi will penetrate, and infected areas will display symptoms that are specific to a particular pathogen.

The most common lawn diseases emerging during the summer months in Wisconsin, the types of grass they infect and their characteristics include:

Brown Patch: becomes active in warm to hot weather when humidity levels are elevated; primarily affects cool weather grasses, but warm weather grasses can also be affected; affected patches are typically circular, growing outward as the disease progresses; in early morning when dew is present, cobweb like substances may appear, a product of the fungi.

Necrotic Ring Spot: can appear summer through fall, as a cooler soil temperature and wet conditions are ideal for infection and subsequent heat, and drought will encourage development; Kentucky bluegrass is most susceptible; identified by circular light brown/ yellowish patches usually smaller than 12 inches in diameter; regrowth in the center can cause a frog-eye type of appearance.

Fairy Rings: essentially these are mushroom forming fungi which occur on all cool-season lawn grasses during warm and wet weather; identified by a ring of dark lush grass bordered by a band of dead turf that may or may not have mushrooms.

Summer Patch: occurs during high humidity in soils with alkaline soil; Kentucky bluegrass and fine fescues are most susceptible; appears as ring-like patches, similar to necrotic ring spot but generally 3 inches in diameter that merge into larger irregular patches; the disease is generally most prevalent with wet springs leading into summer, and symptoms appear when the temperatures rise above 90 degrees.

Dollar Spot: outbreaks occur in high humidity in soils with low nitrogen fertility; generally affect Kentucky bluegrass, perennial ryegrass and fine fescues; manifests as bleached patches up to a foot in diameter with individual grass blades having bleached areas.

Red Thread: outbreaks can occur springtime throughout the fall, favored by cooler wet conditions; affects Kentucky bluegrass, perennial ryegrass and fine fescues; appears as irregular light tan patches that range from a few inches to a few feet that will sometimes merge into irregular shapes with reddish appearing filaments within the blades.

The best prevention from lawn disease is to start with testing the soil, ensuring it has the right PH balance and nutrients that will make it less susceptible. Over fertilized laws may also increase disease damage. It is equally important to have proper drainage for your lawn; sitting water turns into breeding ground for fungi. Proper drainage in addition to early morning watering schedules allow for daylight to burn off extra moisture. Additionally, sharp mower blades prevent the ragged cuts that can both kill grass and allows fungi spores to flourish.

Lastly, fungicides do not always eradicate the targeted pathogenic fungi, but may just reduce them to a manageable level. Once a lawn disease is detected, it is best to seek professional consultation for how to best treat and manage the disease and protect your lawn from further infestation.

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