And this lawn disease lives up to its name. Though often mistaken for Summer Patch blight because of the “frog’s eye” appearance, Summer Patch appears most often in hot weather, while necrotic ring spot shows up during cool weather, especially after periods of prolonged rainfall.
This type of lawn disease can be severe on Kentucky bluegrass and bentgrass, and also takes a stab at ryegrass, red fescue, tall fescue and Chewings fescue. It usually appears in late winter, spring and fall during periods of cool and wet weather. Activity is greater in areas that are not properly fertilized, and Neurotic ring spot lawn disease also tends to show up again and again in areas infected in prior years.
In the early stages, necrotic ring spot lawn disease shows up as roughly circular areas of turf that look like they're suffering from drought, even though there is plenty of soil moisture. You end up with patches that appear to be wilting and drying out when the surrounding turf looks healthy and well-watered. Thatch may decompose quickly in the areas affected by this lawn disease, creating a sunken look to the patch or ring areas. The typical patch of healthy looking turf in the center created the Summer Patch mix-up for years. The disease itself is not active during this phase, but the damage appears because the root system has been destroyed or reduced to the point where it can't support the plant's needs, and so the wilting and drying occur.
The amount of nitrogen fertilizer greatly affects necrotic ring spot development. A minimum of 3 pounds, and preferably 5 pounds, of available nitrogen per 1,000 square feet per season is recommended. It’s also important to provide lawn fertilizing care to keep phosphorus and potassium levels high enough. The Spring Green program delivers the correct blend of nutrients throughout the year, but having a soil test done every 3 years is a good idea to identify any major lawn fertilization deficiencies your particular soil may have. Watering daily during the early to mid-afternoon, with 1/10 to 1/5'' of water, has also been shown to greatly reduce the severity of necrotic ring spot. Should lawn fertilization treatments be needed, they can be applied and are effective if made early in the season: usually 6 weeks to 2 months after the turf goes through its initial green up in the spring.
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