Leaf Spot Lawn Disease On Cool and Warm Season Grasses

leaf spot

There are many different diseases that turfgrasses can contract, but not all turfgrasses get the same diseases, except for one. That disease is called Leaf Spot. There are several different pathogens that cause leaf spot diseases that includes Helminthosporium, Drechslera and Bipolaris. They all belong to a large family of fungi that share the same descriptive name of leaf spots.

The Symptoms and Stages of Leaf Spot

For the most part, the infectious stage of leaf spot fungi occurs during the cool, wet and cloudy weather of spring or fall. Leaf spot can infect all parts of the grass plant; the initial symptoms show up on the grass blades as tan lesions with a reddish-brown border. The term “cigarette burn” is often used to describe the appearance of the lesions. If these cool, cloudy and wet conditions persist for a long time, leaf spot may cause grass blades to turn yellow as the lesions restrict movement of food and water up the grass blades.

The second stage of leaf spot is the more damaging stage. As the disease begins to infect more of the grass plant, the lawn will begin to slowly turn yellow and seem to be “melting” away. This is where the name of the second stage, the melting out stage, gets its name. The melting out stage occurs in early summer when it turns hotter and drier. Many homeowners think that the lawn is just going through some drought stress and will recover once it is watered. If the stem and crown tissues become infected, large sections of the lawn may be affected and recover is a more involved process that may require lawn renovation.

How to Prevent Leaf Spot From Damaging the Lawn

Although you cannot control the weather, you can make sure to follow good cultural practices to help ensure your lawn continues to grow well.

These cultural practices include:

• Increase mowing height to the highest range for the type of grass growing in your lawn.
• Water deeply, but infrequently, to provide 1 inch of water per week
• Do not water in the late afternoon through the evening hours
• Follow a balanced fertilization program that is best suited to the type of grass growing in your lawn
• Core aerate the lawn every year to promote stronger roots and keep thatch levels in check

There are disease control applications that can be applied and will help some if applied when the damage has already begun, but the best control from these types of applications happens when they are applied before the disease cycle begins in the early spring or fall. Keeping the lawn growing well is the best defense against leaf spot becoming a problem in the lawn.

There is another leaf spot disease, Gray Leaf Spot, that is active during warm, humid periods in the summer.This disease is very active on St. Augustine, perennial ryegrass and turf-type tall fescue. Instead of causing circular lesions, this disease starts out as tiny brown dots, which enlarge to irregularly shaped lesions. When humidity levels are high, the lesions taken on a gray tint, which gives the disease its name. The lesions have a distinct brown border between the healthy and diseased tissue.

If you feel your lawn may be having a problem with one of the leaf spot diseases, contact your local lawn care professional at Spring-Green to have them inspect your lawn!

Leaf Spot: Why Does My Lawn Have This Disease?

leaf spot

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.

Lawn Care 101- Are You Up for the Task?

weedy lawn

Pushing a spreader across a lawn is not all that difficult and spraying a few weeds doesn’t take an advanced degree. Here are some things to take into consideration when deciding between taking care of your lawn yourself or hiring a lawn care company to do the work for you.

No offense to my friends who own lawn maintenance companies, but it does not take much expertise to mow a lawn or use a weed whacker. Most homeowners hire a maintenance company because they are tired of doing the work themselves. However caring for your lawn requires more technical knowledge and knowledge of which products to apply and when to apply them.

When I visit my local hardware store in the spring and I see homeowners looking at all of the different weed control products, wondering which one is the best to use, I feel like I should hold an impromptu training session on which product should be used on which plants and on what turfgrasses.

We have all seen the homeowner who picked the wrong product and ended up with lots of dead spots in their lawn because he used a non-selective herbicide, like Round-Up, on his weeds.

Here are some key questions to ask yourself before performing your own lawn care: 

  1. Do lawns in your area have a problem with diseases or insects?
  2. What diseases and what insects are causing the problems?
  3. Are annual white grubs a problem in your lawn or is it chinch bugs or army worms?
  4. Does your lawn suffer from Red Thread, Rust, Brown Patch, Large Patch or Leaf Spot?
  5. What are the correct products to use to treat these insects or diseases?
  6. At what time of the year should they be applied?

Besides buying the right products, you also have to purchase the correct application equipment for the products you plan to use. Make sure to consider these things before heading to the store:

  1. Do you want to use a drop spreader or a broadcast spreader?
  2. Should you purchase a 1-gallon or 2-gallon handheld sprayer or use a hose end sprayer?
  3. What amount do you apply? Most products have labels that provide the application rates, but sometimes the rates are listed as a range, like 4 to 8 ounces per 1,000 sq. ft.
  4. What does a 1,000 sq. ft. look like?
  5. Do you know how big your lawn is so that you can purchase and apply the right amount?

Caring for a lawn may seem like an easy task, but there is a lot more to it than most people realize.  If you want a nice looking lawn, hire a lawn care professional.  It will actually save you money in the long run.

Interested in having your lawn cared for by professionals this spring? Contact your local Spring-Green for more information.