Necrotic Ring Spot is a particularly devastating fungal disease of Kentucky bluegrass, annual bluegrass and fine leaf fescues. Originally, this was called Fusarium Blight because Fusaria was believed to cause the disease. Later research found the causative agent to be Leptoshaeria korrae,. The disease is commonly referred to as “Frog Eye” because it tends to leave round dead spots in the turf that have green grass in the center.
The disease first appears in small patches six inches to a foot in diameter. The soil borne fungi destroy the majority of the turf’s root system in the spring when moisture is plentiful and the temperatures tend to be cool. Even with a severely damaged root system, no symptoms of the disease are evident at that time because the turf can still get the moisture it requires from the cool, wet soils. Once the hot, dry weather of summer arrives, the affected turf tends to wilt and die in the circular patterns described above because it can no longer get enough water to meet its needs.
Chemical control of this disease is spotty at best. Heavy rates of systemic fungicides must be applied and immediately drenched into the soil beginning early to mid spring. Waiting until the symptoms appear is too late because the root damage has been done. Early application of fungicides will reduce the severity or delay disease onset by a few weeks, but will not eliminate the disease or the use of more chemicals. Since these fungicides must be used in heavy amounts, and since they are quite costly, the only thing that a turf manager is likely to do is wipe out his budget. If he is successful in controlling necrotic ring spot, this will only last through the growing season. The following year the disease will reappear.
Nature Safe, on the other hand, offers a complete and permanent control of Necrotic Ring Spot without the use of expensive chemicals. The soil bacteria that Nature Safe feeds and promotes tend to produce anti-fungal compounds that have been shown to inhibit the growth of the Leptosphaeria korrae fungus in laboratory studies. These bacteria are believed to aid in the prevention of new infections in the late summer and early fall. Light frequent irrigation cycles also aid in promoting large populations of these bacteria.
In order to control this disease with Nature Safe, you must apply one pound of actual Nitrogen per 1,000 square feet per month, preferably from 10-2-8 or 8-3-5 for the first year. These applications should begin no later than May 15th and continue until mid-September. Then apply one pound of actual Nitrogen per 1,000 square feet at dormancy. This program is not an immediate cure. After the first two or three applications, a turf manager will see little or no healing to the damaged areas. Late in the season, improvements will be seen and the turf will get progressively better. By the spring of the following year, the disease should be gone. Be careful not to use any synthetic water soluble Nitrogen on the diseased turf because this will cause the disease to get worse. After the first year, you can decrease Nitrogen rates and apply only 1/2 to 3/4 lbs. of actual Nitrogen per application if you so desire.
I can personally attest to the fact that this method works. I had a very bad case of Necrotic Ring Spot on my own lawn that I could not stop with heavy applications of chemicals. I had previously used one of the best forms of synthetic slow release Nitrogen on my lawn for several years. However, each year, the disease got progressively worse. Beginning in the spring of 1999 I began applying Nature Safe 10-2-8 exclusively. By late season, the turf was looking better, but the disease was still evident. By the spring and summer of 2000, the disease was totally gone. Even when the warm weather arrived and the lawn dried up, there were no symptoms of the disease. The best part of this program is that it is a permanent cure, providing that you do not go back to using synthetic forms of water soluble Nitrogen. Overall, a Nature Safe program is much cheaper than applying chemicals, provides great fertility and helps the environment. For more information on formulating a program specific to your area, contact your Nature Safe Regional Sales Manager.