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Leaf Spot: Why Does My Lawn Have This Disease?
Leaf Spot: Why Does My Lawn Have This Disease?
Saying a lawn has leaf spot is somewhat like saying that a person has the common cold. Just about everyone gets the sniffles at some time in their lifetime and just about every lawn will develop leaf spot. Just like with the common cold, leaf spot is usually a minor occurrence. Sometimes the common cold will develop into something as severe as pneumonia and leaf spot may become so severe that a large part of a lawn can die off.
Melting Out
Leaf Spot may progress into a condition called “melting-out”, a condition where the turf just seems to “melt away” as the disease activity becomes more and more severe. Every cool-season and warm-season grass can become infected by different fungi that are all put together under the name of leaf spot. They all share a common trait; a type of mark or lesion that forms on a grass blade. The spots are usually round in shape and as the disease progresses, the spots develop a reddish-brown border. They may enlarge to a point where the blade or stem are girdled, which may lead to the demise of the grass plant. When enough of this activity occurs, the turf enters into the “melting out” stage and the turf often thins out.
When Are Leaf Spots Active?
Leaf spots are active during the wet, cool weather of spring. Kentucky Bluegrass is the most susceptible of the cool-season grasses, but Perennial Ryegrass, Tall Fescue, Fine Fescue and Bentgrass can all become infected. Warm season grasses will contract these same species of leaf spot. There is another disease that carries the same leaf spot name, but occurs in the summer during periods of high heat and humidity. This disease is called Gray Leaf Spot. It can infect Perennial Ryegrass, Tall Fescue and St. Augustine grasses.
Leaf spot can be aggravated into activity by applying too much or not enough nitrogen fertilizer. Do not apply nitrogen at a rate above 1 pound per 1,000 sq. ft. in the early spring. If you use a lawn care company, don’t supplement their applications by applying more nitrogen in the spring. Keeping the lawn mown at the right height is also very important. Also, do not water in the evening, as this sets up prime conditions for leaf spot to develop: cool, dark and moist. If leaf spot in your lawn does develop into the melting out stage, applying a disease control treatment at that time will probably produce little results.
Proper Care
For cool-season grasses, follow the proper care for your lawn during the summer and then core aerate and overseed in the late summer to early fall with leaf spot resistant seed. In warm season areas, the grasses will usually grow out of the disease, but having the lawn core aerated will help the lawn recover faster. If leaf spot is a re-occurring problem in your lawn, applying a disease control material before the lawn enters the melting out stage is the best practice.
If you are not sure if your lawn has a problem with leaf spot or melting out, contact your local neighborhood Spring-Green lawn care professional. They will be able to provide the best recommendations to help your lawn improve.