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We know that it’s always better to prevent a disease rather than try to cure one. That goes for the diseases that infest your lawn also. But try as you might, there are times you just can’t. You might over-water or under-water. Or cut the grass too short. Or fertilize it improperly. Your grass gets stressed, same as we do, and then it’s also more susceptible to disease. Stressed lawns are a “Y’all come!” to lawn diseases, and once they settle in, they can cause serious damage.
Learn to recognize the following five diseases common to Tampa lawns and you can take the proper actions sooner rather than deal with rehabilitating your lawn later, when it may be too late.
Photo: John Kaminski
Brown Patch Fungus
Brown patch usually starts in a small area of the lawn. The leaves turn yellow, then reddish-brown, then straw-colored as they die. It’s an aggressive fungus and will spread into patches up to several feet in diameter, particularly in the fall and particularly on St. Augustine and Zoysia lawns. There are a few distinguishing characteristics of brown patch: small tan spots with dark brown borders on the leaves, circles of brown or dead grass surrounded by a narrow dark ring, or rings of yellow-brown grass surrounding healthy grass.
Brown patch erupts due to heavy rainfalls for a long period of time or the lawn is being seriously over-watered, generally from November through May, when temperatures are below 80 degrees.
Photo: John Kaminski
Folk tales tell of fairies dancing in a circle at night and sitting on their toadstools in between dances. It’s a charming story. Fairy ring lawn disease is not.
In Tampa (and all over Florida for that matter), fairy rings appear year after year, always in the same spot. You’ll see 3-foot to 20-foot rings of dark green or dead grass, most often in hot weather and heavy rainfalls. Sometimes there will be mushrooms in a circle or semicircle, but not always.
Fairy ring spreads rapidly along the root system of the grass, depleting the nitrogen that is essential for the life of the grass. It also has a second line of attack. It produces mycelium (a web of fine white threads), which, as it dies, hardens and kills the grass by keeping water from reaching the roots.
Fairy ring is kind of sneaky. By the time you see the signs, it’s been in your soil for two to three years. Then, you think you’ve taken care of the problem and it’s back several years later.
Photo: John Kaminski
Dollar spot appears in a pattern of dead circular patches about the size of a silver dollar. A spot by itself doesn’t look too ominous. Don’t let it fool you. Those small patches become very large areas, and dollar spot is merciless. It kills the grass right down to the roots.
You can also identify dollar spot by the lesions (infection marks) on the leaves of the grass. They begin as light tan with a reddish-brown border and turn white to straw-colored as the lesions grow into one large leaf blemish. Another clue is when you see mycelium early in the dewy morning.
Dollar spot starts growing when the humidity is high and temperatures reach into the 60s and is most active when they rise above 70 degrees.
Rust fungus is a yellowish-orange powder that turns your lawn to yellow, orange, red or brown. In the beginning stages, leaves develop yellow flecks that get larger and become dark yellow. By then, the flecks are pustules that burst and release spores that are the powder you see.
When the infection is severe, the leaves will turn rust-colored, and growth slows down considerably, the lawn becomes sparser and individual leaves begin to die. Or leaves become shredded and droop. However it presents itself, the primary danger is that your lawn is susceptible to more lethal lawn diseases.
Rust attacks grass that is in the shade and stays saturated with water from rain, dew, humidity or due to your watering it too often. Be on the lookout from early spring to fall when temperatures are between 60-85 degrees, particularly if your grass is growing more slowly than usual.
Photo: NC State
Grey Leaf Spot
Grey leaf spot looks like brown patch fungus at first, but it attacks the tops of the leaf, leaving tiny olive-to-brown oblong spots, which may have grey “velvet” growths in their centers. As the disease progresses, the oblong spots become oval or an irregular shape.
Grey leaf reduces the ability of the grass to thrive, making it sparse and spindly. It most often occurs from early spring to early fall when the humidity is high and rainfall is heavy (or you’ve over-watered).
The moist Florida climate allows spores to produce with abundance.