Chinch bugs (Blissus insularis) can be a serious problem for anyone who has a lawn, whether it’s a small backyard or a large grassy field. Chinch bug damage typically appears first as brown spots in the lawn and may be mistaken for other problems, such as drought damage or winter stress. If not stopped, chinch bugs will continue to feed on the grass until the entire lawn is dead.
How Chinch Bugs Feed
Chinch bugs live down in the thatch of the lawn and feed by poking their long, slender, beak-like mouths directly into grass stems and sucking out the juices. These pests also cause damage by injecting their saliva into the stems. Chinch bug saliva is toxic to plants, increasing the damage that they cause when feeding. Chinch bugs are particularly fond of St. Augustine grass (Stenotaphrum secundatum), which grows in U.S. Department of Agriculture plant hardiness zones 8 through 10, but according to the University of Nebraska’s Department of Entomology, chinch bugs will also eat other grasses such as buffalograss (Bouteloua dactyloides), hardy in USDA zones 5 through 8, and zoysiagrass (Zoysia spp.), found in USDA zones 5 through 10.
Identifying Chinch Bug Problems
The best way to tell if you have chinch bugs is to look for these small bugs in your lawn. Nymphs are red with a white banding across their back, while adults are black with or without wings and approximately 1/10 inch long. Cut off both ends of a coffee can and push one end several inches down into the soil around a patch of yellowed but not dead grass. Fill the can about half full with water and see if any chinch bugs float to the surface within five minutes. Another way to find them is to mix 1/4 cup of dish soap into a 2 gallon watering can and mix well. Saturate a 1 square foot area of the lawn and watch for the bugs to rise to the surface of the lawn within approximately two minutes, according to Seminole County Extension Services.
Cultural Control of Chinch Bugs
One of the best ways to deal with chinch bugs is to make your lawn unattractive to them. Both over-watering and over-fertilizing will cause your lawn to develop a thick thatch, making it very appealing to cinch bugs. Instead, water your lawn deeply but allow it to dry out between soakings. Fertilize moderately, with a slow-release nitrogen fertilizer, and only when your lawn needs it. If thatch builds up in the lawn, rake it vigorously to remove it, and mow grass often during the growing season to minimize thatch buildup, removing no more than one-third of the blade at each mowing.
Treating Lawns for Chinch Bugs
Applying a pesticide containing bifenthrin or carbamate is an effective way to kill chinch bugs provided the thatch is not so thick that it shelters them. Pesticides are typically applied at the rate of one quart chemical to 15 to 20 gallons of water for 1,000 square feet of lawn. Biological controls can also be very effective against chinch bugs and have the added advantage of not killing beneficial species along with the pests. Big-eyed bugs (genus Geocoris) and minute pirate bugs (genus Xylocoris) are two important chinch bug predators and may be purchased from some biological control supply houses. Many wasps, spiders and ants also prey on chinch bugs. Before applying any pesticides, mow the lawn and rake away any grass clippings. After the pesticide application, water to a depth of 1/8 inch to wash the pesticide residue off the grass and filter it down into the grass crowns to reach the area of the grass where the chinch bugs are feeding.