Chinch bugs (Blissus) are a pest comprised of four species that attack lawns across the United States. The bug eats its way through grass down to the thatch, sucking out fluids and killing yards in large patches that resemble drought damage. A secondary problem occurs when weeds can then take over. Chemical controls can help keep them in check, as can a focus on lawn health.
Know the Enemy
Get down and look for chinch bugs first, as the brown patch in your lawn may be drought stress or brown patch disease. Adults have bodies that are small, thin and black, their white wings marked with a telltale triangle. The babies, or nymphs, are wingless; their pink or yellow bodies have a band of lighter color. Chinch bugs are not limited to St. Augustine grass. They can also chomp their way through centipedegrass, bermudagrass, zoysiagrass and bahiagrass. They hibernate over the winter, but begin procreating in the spring -- and do so quickly. Each female can lay up to 300 eggs, which hatch within 14 days.
Count the Enemy
Determine how many bugs are in a small area of grass to determine how large the problem is -- as well as how much pesticide you may need to fight them off. Cut the ends off a metal can and push one end of it into the soil, up to 3 inches deep, where the infestation appears but the grass is not completely dead. Slowly fill the can with water. Chinch bugs will float to the surface when present. Count how many bugs you see within five minutes. If nothing appears in the first spot, test several more to determine if chinch bugs are present. If they are present, test several areas of the devastation to get an average bug count. The University of California, Davis, says you should begin treatment when you find three chinch bug adults or nymphs in the water. According to the University of Maryland, 15 to 20 chinch bugs per square foot should provoke your declaration of war against them.
Attack the Enemy
Go after the cinch bugs as soon as you confirm they are the cause of your lawn's demise, usually in early summer. Use a fast-acting pesticide that contains a pyrethroids (similar to a plant toxin) such as beta-cyfluthrin, Bifenthrin or lambda-cyhalothrin. Any of these three should remove up to 90 percent of the chinch bugs in less than a week. Follow the manufacturer's directions on how much to apply, and the application technique. Liquid forms may be sprayed on the affected area, while granular forms can be applied with a lawn spreader. A second application may be applied in mid- to late summer if a reemergence occurs. A slower-acting pesticide containing a neonicotinoid insecticide (a neuro-toxin) take longer, but can last up to 100 days in the lawn, fending off any return of the unwanted bug.
Repel the Enemy
Keep your lawn unattractive to chinch bugs during the growing season by keeping it free of thatch, an accumulation of dead grass providing shelter to the pests. Rake the yard to remove thatch in the spring or any other time it appears to build up. Mow the yard frequently and keep it short. Mulch or bag grass clippings to stop thatch from forming. Avoid over-fertilizing, which creates more thatch to attract bugs. Aerating the yard -- punching holes in the soil with a special machine -- in the fall or spring discourages thatch buildup, as well.