How to Get Rid of Brown Spots on St. Augustine Grass
Aerate your lawn to improve circulation and make it a less hospitable environment for fugus.
A lush green lawn tempts you to walk through it barefoot or to stretch out for a quick nap in the sun. That expanse of emerald grass is restful and beautiful. But brown spots mar the beauty, standing out like moles on the face of a pageant queen. Treat brown spots promptly to prevent them from spreading. Soon you will be enjoying all that green perfection again.
Determine the cause of your brown spots. The four most likely causes are brown patch, take-all patch and chinch bugs. Brown patch and take-all patch are fungi. Brown patch usually occurs in the spring or fall and occurs in lawns that are over watered or in areas of the lawn that don’t drain properly. Brown patch may resemble a donut with a spot of green inside a circular area of dead or dying grass.
Take-all patch occurs most often in summer. The take-all patch fungus kills the entire plant.
Grubs eat the grass roots and are more prevalent in summer and autumn. A lawn infested with grubs will have patchy brown spots. The dead grass comes up easily in patches when you tug at it. Dig down into the soil, and you should find the grubs.
Tiny chinch bugs suck the juice from the grass blades. Damage may resemble a grub infestation, but if you tug on the dead patches, the grass doesn’t come up easily since chinch bugs leave the roots intact. Brush your hand through the grass, and you should see tiny white bugs.
Treat the lawn to kill the fungus or pest that’s killing the grass. For brown patch, spray with a fungicide designed to kill the fungus. Don’t overspray or allow the fungicide to run off into ditches or the street.
Take-all fungus is much harder to kill. Cover the brown spots with a ½-inch layer of sphagnum peat moss. The peat moss makes the soil more acidic and inhospitable to the fungus.
By the time you spot grub damage, it’s probably too late to do anything. The grubs are the larvae of beetles and by summer's end will be transforming into beetles which will return in the spring to lay their eggs. Make a note to apply a granular soil insecticide next spring to kill the grubs before they hatch.
Treat chinch bugs with the same soil insecticide you would use for grubs.
Re-sprig any dead areas of lawn once you’ve killed off the cause of the problem. Avoid over watering and improve drainage in any areas where water tends to stand. Water in the early morning so the grass has time to dry before nightfall. Use slow-release fertilizers and avoid using too much nitrogen.