Necrotic Ring is a disease that typically affects lawns during the hottest months of the year, when the grass is under the most stress. It can be identified by donut-shaped rings between one to five feet in diameter. These patches can be localized or seen throughout your lawn.
This disease is caused by a fungus known as Ophiosphaerella korrae, and is common in areas with poor drainage and compact soil. Over watering is another common instigator that will encourage the growth of this fungus.
There are some types of grass that are more resistant to Necrotic Ring than others are. Rye grass and certain types of Kentucky bluegrass are resilient and will resist the spread of Necrotic Ring. In fact, you can seed affect areas of a lawn with rye grass seed to encourage lawn growth.
Other ways to prevent the growth and spread of Necrotic ring are good lawn maintenance practices and prevention. Good lawn maintenance includes not overwatering your lawn, and only mowing the top 1/3 of a blade of grass at time by using the second highest setting on your lawn mower. Be cautious when applying fertilizer that is high in nitrogen to help curb the growth of Necrotic Ring and use slow release fertilizers over multiple application over the summer months.
Applying fertilizer in the late spring and early fall can help reduce the growth of Necrotic Ring, and applying Sulfur amendments when fertilizing can also help prevent the growth of fungus on your lawn.
If you decide to apply a fungicide, you need to make sure you time the applications carefully to get the proper affect. Apply the first dose in approximately mid-May, followed by a second application in the middle of June. This makes sure that the fungicide is still working during the peak time when fungus grows on your lawn.
With careful planning and maintenance, you can prevent Necrotic Ring and other diseases from affecting your lawn, and keep it healthy all year round.