Brown Lawns caused by a leaf blight

Ascochyta, 6-2018

Symptoms from Ascochyta Leaf Blight

This year has been difficult for our lawns. Since our cold April, our temperatures skyrocketed and we haven’t had many rain events throughout this spring and early summer. This has been causing our lawns to look a little ragged and brown.

Ascochyta

Many cool season lawns throughout Eastern Nebraska have begun to look brown due to Ascochyta leaf blight, a widespread disease found throughout the early part of summer this year. Mowing during the hot Memorial Day weekend seemed to have worsened the symptoms of this disease.

Symptoms

Ascochyta close up, 6-2018

A close-up of the blades of turf infected by Ascochyta

Ascochyta is a diseased that is stress-induced and often shows up in the early summer when the weather shifts from cold and wet to hot and very dry. Ascochyta is a dieback from the tip of the leaf blades of cool season turf. Red-brown spots can also appear lower down on the affected blades. You might also notice a dark brown/black band between green growth and the brown tip of the blade. After the initial disease moves through, a general brown appearance will show up in the lawn, often following lawn mower tire patterns. Mowing worsened the symptoms of this disease, not by spreading it, but by the physical traffic of the equipment  to weaken the turf. This allowed for ease of the fungus to attack the lawn.

Ascochyta affects just the turf blades of the plant, not the roots or crown of the plants. The crown is the growing point of the turf. Because it doesn’t affect the roots and crown of the plant, it is then able to grow out of the disease. Mowing the lawn will remove the infested areas of the plant which will lead to regrowth and regreening of the lawn over time.

Management

There are a few types of fungicides labeled for use on ascochyta, however, research at UNL shows poor results with many different classes of fungicides on this disease. The best management for Ascochyta would be to reduce stress and manage the lawn properly. Provide adequate moisture for the lawn. Remember it is best to provide 1-1.5 inches of water per week to the lawn. If that isn’t provided through rainfall, irrigate two to three times per week with 1/3-1/2 an inch each time to keep the lawn healthy. Also, ensure that your lawn mower blades are sharp to avoid tattering the leaves which can leave more of an opening for diseases to move into grass plants. Finally, early June is a great time for a slow-release fertilizer to help slowly feed your lawn through the summer months and keep it healthy.

For More Information

The information for this news article on Ascochyta came from the UNL Turfgrass Team of Bill Kreuser and Roch Gaussoin. This information came through a Turf iNfo update. You can sign up to be on their listserv to receive these updates automatically as they come out by going to the Nebraska Turfgrass Website and scrolling down to click on the ‘SIGN UP FOR TURF INFO’ tab at the bottom of their page.

 

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