Cool Weather Lawn Problems by Charles Bohmfalk
We are now entering the fall season that brings cooler weather and humid, rainy conditions. Lawn diseases become a bigger problem with these conditions that are more pleasant for us. Brown patch is one of the lawn diseases that becomes a problem in our lawns during the cooler and more humid weather conditions in the fall and early winter months when night time temperatures are below 70° F and the daytime temperatures are in the 75° F to 85° F range. Most turf grasses are susceptible, especially St. Augustine, zoysiagrass and centipede grasses. Brown patch doesn’t normally kill the affected grass, but it can weaken the affected grass and make it more susceptible to further damage by the approaching freezing and sometimes dry winter conditions. Brown patch is a fungal disease problem that can easily be confused with grub worm, armyworm, sod webworm, cutworm and chinch bug damage. Proper diagnosis is necessary to treat and remedy the problem.
Brown patch has circular to irregular shaped patches of brown or yellowing grass that is less than one foot to several feet in diameter. The outside of the circle may have a “smoke ring” appearance that is caused by the spreading fungus. In this area, the leaves of the grass may be easily pulled from the stolens or stems. Inside the infected area the grass may remain green that leaves a “frog-eye” appearance. Leaf sheaths in the infected area also become rotted and water-soaked to the point that a gentle tug of the leaf blade easily separates it from the runner. To prevent this disease from attacking your lawn, pay close attention to your watering habits, thatch accumulation, and your nutrient management program. Fungicides that are easily obtained at your local garden center can be used for the prevention and control of brown patch. Read the label and carefully follow the directions when using any fungicide or insecticide.
Brown areas caused by grub worms will show a browning or the appearance of a lack of water in the area. The damage may be a small spot or cover a large area and is caused by white grub worms, the larvae of the May or June bugs. The larvae feed one to two inches below the surface and destroy part or most of the root system of the lawn. Damage usually appears in late July through early August. If the damage is heavy, the sod can be easily lifted up or rolled up. To verify that the problem is grub worm damage, dig one square foot sections to a depth of 4 inches. Treatment with an insecticide is necessary if more than four grubs are found per square foot.
Cinch bug damage appears as irregular patches in sunny areas, usually along driveways, sidewalks and house foundations. The grass first turns yellow and eventually dies and then turns brown. To identify a chinch bug infestation, remove both ends of a metal can and twist it into the grass. Fill the can with water and a little detergent. In a few minutes, the chinch bugs will float to the surface. They are black with white wings folded over the body. Treat with an insecticide that has cinch bugs listed on the label. Read the label and carefully follow the directions when using any fungicide or insecticide.