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Necrotic Ring Spot – The Frog Eyed Disease

What is a Necrotic Ring Spot?
Necrotic Ring Spot is a common disease found in cool-season grasses, primarily Kentucky Bluegrass, but also different types of fescues. It is caused by soil borne fungi (Leptosphaeria Korrae), which will mainly attack the roots. 

What does Necrotic Ring Spot look Like?
It is a very noticeable fungus as it destroys the appearance of the lawn by causing yellow/brown rings, with healthy grass in the middle. Some people say it gives a frog eye appearance.

This is a close up of Necrotic Ring Spot. As you can see the ring gives the appearance of a frog eye
This is a closeup of Necrotic Ring Spot. As you can see there is a brown ring with healthy grass inside the ring. Almost looking like an eye
This is an image of Necrotic Ring Spot
As you can see in the image. Necrotic Ring Spot creates rings.
This is an image of Necrotic Ring Spot on cool season turf.
This is an image of Necrotic Ring Spot on cool season turf.

 

How does Necrotic Ring Spot affect your lawn?
It has been known to be a devastating and aggressive fungus that is hard to control as it will colonize the roots and crown. The spores will transfer by soil and turf contact from one part of the lawn to another. This fungus can survive unfavorable conditions in plant debris and is thought to be able to move from plants by growing on the surface of the roots and rhizomes. This infection within the roots will result in a decrease in water and nutrient uptake. Which will then cause the roots to be more prone to other injuries, especially during heat and drought stress.

What is the life cycle of Necrotic Ring Spot?
This fungus usually will infect roots, rhizomes, leaf sheaths and crowns of turf in spring or fall. Symptoms of this disease will be present in late spring during cool-wet weather conditions. Some areas may fade with temperatures rising going into the summer months, but some areas will appear because of heat or drought stress. In fall months the infected areas will reappear and at times can continue throughout winter and into early spring. The recovery time from this disease is very slow and can take years to fully recover. 

How to maintain/cure Necrotic Ring Spot?
There are a few methods to maintain this fungus or to completely get rid of it. You can water lightly as the disease rings contain dying grass which is caused from the rotting roots being unable to uptake nutrients and water. You can raise the height of your mower. Aerating the soil can also help to take out parts of the disease manually. The best method of treatment is going to be applying a fungicide treatment. You may need to persistently apply this year to year or multiple times a season. This disease is a slow recovering disease and can be very stubborn when trying to get rid of it. 

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