Lawn isolated brown spots

What to do about ring spots on your lawn?

This time of year, you may be noticing the development of rings or dollar-sized brown spots on your lawn. This is referred to as ring spot or dollar spot and more formally as Necrotic ring spot (NRS).

NRS is a disease of lawns that creates dollar-coined-sized or larger circles of dead grass throughout your lawn. It is a chronic fungal disease treated in mid-spring.  Because we’ve received questions about NRS recently we wanted to encourage you to take the following actions to get your lawn ready for a treatment for this fungal condition.

Necrotic ring spot.

Necrotic ring spot.

Since NRS becomes more apparent in the hot days of summer but it’s best treated at the beginning of the growing season,  it’s important to help keep NRS under control until next spring. It can be an extremely frustrating lawn care issue and it looks worse this time of year.

In fact, you’d think the lawn would get greener with rain but with NRS the opposite tends to happen. In fact, that is one of the signs a good lawn service looks for in diagnosing an under-performing lawn.

Luckily, with patience and consistency, it can be brought under control, if the exact treatments are executed properly and if the weather cooperates.

Here are some tips for what to do now with your Denver lawn care in summer, to set it up for direct treatments next year.

  • Do not overwater. This is perhaps the most important management practice for NRS. It is tempting to irrigate lawns with a history of NRS more frequently. However, this will enhance the disease. Water the lawn to a depth of 6 to 8 inches as infrequently as possible, usually no more than twice a week, without creating water stress. Also, check to make sure irrigation heads are working properly and limit inefficient zone coverage that may create puddles in the yard.
  • Follow good management practices on established lawns. Maintain the turf at a height of 2 ½ to 3 inches. Remove no more than 1/3rd of the blade at any one mowing.  Also, make sure that lawn mower blades are sharpened. Since the NRS pathogen attacks the roots and not the leaves, it is not spread by mowers. Returning clippings with a mulching mower may actually help turf recovery by recycling nitrogen during the leaf decomposition process. Core aerate established lawns at least once a year (spring or fall) to help reduce thatch buildup and improve soil drainage. Core aeration equipment may spread the NRS fungus although this is not likely a major means of pathogen movement. Furthermore, the benefits of aeration outweigh potential problems.
  • Fungicide timing. Fungicide timing is critical for disease control. Products must be applied in spring before root colonization by the fungus is established. Make an application in May when soil temperatures reach 65° F at a depth of 2 inches. This usually occurs in late April, or May. Do not make the first application too early in the spring because fungicide control may dissipate before the fungus starts colonizing roots. Make a second application after one month. A third monthly application may be necessary on severely damaged lawns. Applications after symptom development or in late fall are not effective. Lightly water the fungicide into the turf (less than ¼ inch) but do not drench the lawn. Fungicide applications only suppress NRS; they do not eradicate the NRS fungus. Therefore applications over several years may be necessary to manage NRS on severely damaged lawns.

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