Commercial Lawn Disease Control

Understanding Necrotic Ring Spot and Ascochyta

Commercial lawn disease control for large-scale properties which can suffer from large-scale turf diseases. Left untreated, they can spread and become even more difficult and costly to treat. It is in the best interest of your property to treat your lawn at the first sign of trouble.

Since 1947, Swingle has been working to keep Colorado commercial property lawns healthy and disease-free. But lawns, like people, can suffer from stress. Dead patches or brown rings, which can be a sign that your lawn needs our help.

Does your Lawn Suffer from Dead Spots or Dead Patches?

Necrotic Ring Spot Control

The most common Colorado lawn disease is Necrotic Ring Spot (NRS), a perennial lawn fungus that causes round or doughnut-shaped patches of dead grass. This soil borne fungus affects Kentucky Bluegrass. Although NRS thrives in our arid climate and weather conditions, it can be controlled by the use of resistant varieties, good turf management practices and fungicide applications.

Necrotic ring spot, lawn care disease

Necrotic Ring Spot (NRS) is a fungal disease affecting stressed lawns and is active from May until October. NRS first appears as small, scattered, straw colored patches. As it progresses, the rings become crater like scars. Often tufts of green grass remain in the center, giving the lawn a frog eye appearance. Swingle’s Marathon program, along with your everyday good lawn care practices, can better suppress this disease.

What we do:

Aeration: NRS is a soil born fungus that damages the root system of your lawn. Aeration loosens up the soil to allow air, water, and nutrients to penetrate the root-zone. This promotes additional growth speeding lawn recovery. We recommend aeration for NRS affected lawns twice a year, during the spring and fall months.

Fertilization / Weed Control / Insect Control: Our patented, programmed released fertilizer provides superior results in our Marathon NRS program over other fertilizers. Our fertilizer releases slowly and is only applied once in a growing season. The slow release of nutrients helps the grass grow steadily promoting healthy root growth while maintaining a green lawn.

Fungicide Treatment: For moderate to severe disease, we recommend a fungicide treatment that must be applied one time per year in the spring. Improving your lawn’s condition from NRS requires staying consistent with your recommended NRS program. Results are not immediate, it requires a minimum of 2 years of recommended treatments for suppression of this disease.

What you do:

Mowing: The highest setting on your lawn mower will help shade the soil, keeping the roots cooler in the hotter months. A taller lawn height also conserves moisture and promotes lateral growth to thicken the lawn. A sharp mower blade will also improve the general health and appearance of the lawn. (2 1/2” to 3” mow height)

Watering: During the growing season two fifteen minute watering cycles, once in the morning and once in the evening are recommended for areas of your lawn suffering from NRS. Watering during over winter and during dry periods is critical to reducing the stress which aggravates NRS.

Reseeding: Often over-seeding with a blend of disease resistant seed will help re-established your lawn in damaged areas. We recommend a blend containing perennial ryegrass.

Results: We do not guarantee control for Necrotic Ring Spot. We have found, however, that improved lawn care practices can greatly reduce the scarring that occurs. Following our recommendations for both lawn care practices and treatment will help suppress NRS damage. In turn, this will encourage new growth which will fill in old NRS scars and improve your lawn’s health and appearance.


Ascochyta – Kentucky Bluegrass Fungal Disease

Ascochyta is another common lawn disease. A fungal disease that occurs with Kentucky Bluegrass, it’s most prevalent in the spring and summer when lawns are stressed due to variable moisture conditions and temperature fluctuations. It can occur throughout the growing season.


Individual blades start dying back from the tips, withering towards the base of the grass blade causing the leaf tip to appear pinched. In most cases, pockets of infection will cause a patchy or streaked appearance.

The area will recover in 2-3 weeks with additional watering and mowings.


What can be done?

  •      Core aerate to reduce thatch buildup.
  •      Keep mower blades sharp.
  •      Mow grass to a height of 2 1/2 to 3 inches.
  •      Water in the morning so leaf blades can dry quickly.
  •      Water the affected area with more water less often.
  •      Use a soil conditioner such as REVIVE to improve your lawns water efficiency.


If you believe you have a lawn disease on your property, contact Swingle immediately.