LAWN ALERT: St. Augustine Grasses Under Attack From Grey Leaf Spot Disease

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It looks like another Grey Leaf Spot infestation has begun this season in Tallahassee. We recently uncovered this while examining St. Augustine grass blades with leaf lesions.

They had lost their green color, and the lawn looked thin and had a delicate appearance in spots. With the frequent warm rains we’ve been getting recently, it always creates this favorable environmental for this nuisance fungal disease to show up unannounced, grow, and spread.

The Dickerson Landscaping technicians started noticing that all too familiar oval and oblong-shaped grey leaf spots on the blades of grass.

Our teams are finding more and more instances this season where the pathogenic organism Grey Leaf Spot is on the loose and devastating local St. Augustine grasses. So, we needed to get the word out to you and the community.

What causes Grey Leaf Spot disease?

With the introduction of warmer rains in our region, from May to September, there is a specific fungus that will begin to spawn. When the St. Augustine leaf blade remains wet for 12-hours or longer, and the air temperatures linger between 80 and 90 degrees this pathogen will grow, infect, and colonize the turf.

With Grey Leaf Spot, you have the fungus Pyricularia grisea, also known as Magnaporthe grisea to blame, which is responsible for its creation. Interesting enough of all the warm-season grasses in our area, it is the St. Augustine grass and only this grass that is affected by this disease.

What are the disease symptoms to look for in your St. Augustine grass?

Besides the oval and oblong-shaped grey leaf spots on the grass blades, you will also notice what we call “Sporulations.” In the center of the leaf spot, it will have a felt-like formation of spores. You might also find the leaf spot is olive green or brown with a dark brown border. That indicates sporulation is no longer present.

However, at this stage, many of the spots may have already merged and turned entire blades or shoots of grass brown. You will begin to notice your lawn has started or lost its robustness. The grass sprigged areas will have slow grow-in and reduce any chances of the St. Augustine grass recovering. That’s when you know the disease has taken hold of your lawn.

Could your Leon County lawn be ripe for this years’ infection?

Here’s what you’ll want to know before it happens to you. Now that you know St. Augustine grass is a prime target for Grey Leaf Spot disease; it’s time to review disease management.

As a homeowner or property manager, here are four easy tips, you must remember before you’re forced to purchase and install new sod to repair the turf damage.

  1. Every year we have a heavy rainy season from May to September, and that’s when St. Augustine grass is most susceptible to infection.

  2. There is no known St. Augustine grass cultivar currently marketed that is entirely immune to Grey Leaf Spot disease.

  3. Proper and timely irrigation management should relieve any drought-stressed turf without creating a fungus environment.

  4. Carefully consider when the timing is appropriate to apply any atrazine application because it could invite severe Grey Leaf Spot symptoms when temperatures rise above 85 degrees.

For more information about St. Augustine grass care, we invite you to give Dickerson Landscaping a call, and you can speak to one of our lawn care specialists for further assistance.

If you found “LAWN ALERT: St. Augustine Grasses Under Attack From Grey Leaf Spot Disease” helpful, then check out our other article, “Is It Time To Plant Your Thank You?