Beyond the big three — large patch, brown patch and gray leaf spot — North Florida lawns produce a collection of smaller conditions that alarm people out of proportion to the damage they cause. Some genuinely need attention. Several are harmless and only need to be recognized so you stop treating them.
Dollar spot
Small, roughly silver-dollar-sized bleached or straw-colored spots, which merge into larger irregular patches as they multiply. Look closely at individual blades and you will see lesions that go straight across the blade, bleached in the middle with a darker border. In heavy dew you may see fine white cobwebby growth early in the morning that disappears as things dry.
The useful thing about dollar spot is what it tells you: it is strongly associated with low nitrogen. It is one of the few turf diseases where the lawn is genuinely underfed. It also favors heavy dew, extended leaf wetness and drought-stressed turf.
Response: a modest nitrogen application on an underfed lawn frequently resolves it. Water deeply in the morning so the canopy dries. Note the tension here, since on centipede you have to be careful not to overcorrect. Centipede wants very little nitrogen, so a light application is the right move rather than a heavy one.
Fairy ring
Rings or arcs of dark green, fast-growing grass, sometimes with mushrooms around the edge, and sometimes with a ring of dead or thin grass instead. The cause is fungi living on decaying organic matter in the soil, frequently old buried wood, stumps or construction debris.
The dark green ring is where the fungus is releasing nitrogen as it decomposes material. The dead ring version happens when the fungal growth becomes so dense it makes the soil water-repellent, and the grass above it dies of drought while everything around it is fine.
Fungicides are generally not effective and not worth the money. The practical responses are to mask the ring with light fertility so the color evens out, and to deal with the water repellency by aerating the ring and watering deeply, sometimes with a wetting agent. If it is caused by a buried stump, the ring will persist until the wood is gone.
Slime mold
Alarming and completely harmless. It appears overnight after warm wet weather as a gray, white, purple or yellow crusty or powdery growth coating the grass blades, often in a patch a foot or two across.
Slime mold is not a plant pathogen. It is using the grass blades as a surface to grow on and is feeding on bacteria and organic matter, not on the grass. It looks like something serious and it is doing nothing.
Response: hose it off, mow it off, or wait for dry weather and it disappears. Do not spend money on fungicide for this.
Algae
A dark green to black slimy film on the soil surface in areas that stay persistently wet and shaded, which dries into a crust that sheds water and prevents grass from establishing.
Algae is a symptom, not the disease. It appears where there is too much water, too much shade and too little air movement. Treating the algae without fixing those conditions accomplishes nothing.
Response: fix the drainage, reduce irrigation to that area, open up the shade by thinning limbs, and relieve compaction. Break up the crust with a rake so water and air get in. Then decide honestly whether turf belongs there at all, since a permanently wet, shaded spot may be better as a bed.
Mushrooms
Mushrooms in a lawn are the fruiting bodies of fungi decomposing organic matter in the soil, usually old roots or buried wood. They are not attacking the grass and they mean the soil is biologically active, which is generally a good sign.
Knock them over or mow them off if you dislike them, particularly if you have children or pets, since some are toxic if eaten. They will keep appearing after wet weather until whatever they are decomposing is gone. No treatment is warranted.
The pattern in all of this
Notice how many of these come back to the same short list: too much water, poor drainage, too much shade, not enough air movement, and nitrogen either too high or too low. That is not a coincidence. Nearly every lawn disease in this climate is driven by moisture management and fertility.
Which means the same handful of habits prevents most of them. Water deeply and early in the morning. Turn the system off during rainy stretches. Keep nitrogen appropriate to the species, which on centipede means restrained. Improve air movement and light. Fix wet areas. Mow at the correct height with a sharp blade.
When to get help identifying something
If a problem is spreading and you cannot identify it, your county extension office can. UF/IFAS Extension handles turf diagnostics routinely, and a correct identification costs far less than treating the wrong thing twice.
We are also happy to look at something while we are on a property and tell you honestly whether it needs attention or whether it is harmless. Get in touch anytime.