Updated: Sep 15, 2020
If you’ve been watching your lawn develop brown patches over the summer, those dead spots are likely caused by one of three things: lack of water; Take All Root Rot (TARR); or chinch bugs.
Process of Elimination
Fortunately, it’s easy to tell which of problem you’ve got. First make sure your sprinklers are working properly and watering evenly, and, if necessary, have them repaired.
TARR is a fungus that generally gets started due to excess moisture. Again, this could be brought on by over-watering, but this summer’s exceptionally hot, dry weather means it’s probably chinch bugs. The little buggers are especially bad this year and have been destroying lawns all over North Texas.
What’s a Chinch Bug?
Chinch bugs thrive in the heat and sun, and particularly enjoy feeding on St. Augustine lawns, although they are also happy to kill Bermuda, Bahia, Zoysia and other grasses. They spread fast across your lawn using their sucking mouthparts to remove sap from the base (crown) and stolons of plants and inject a toxic substance that prevents the plant from transporting water. The Texas A&M AgriLife extension Field Guide to Common Texas Insects offers details on chinch bugs and their life cycle.
Photo: Chinch bugs in various life stages from nymphs to adults.
The Chinch Bug Test
Fortunately there’s a quick and easy way to quickly tell if your problem is chinch bugs.
1. Grab a coffee can, soup can or other metal can and open it at both ends. (A larger can is better, as it’s easier to see and it gives you a larger sample area.)
2. Choose a spot along the edges of the damaged area, rather than in the middle of a dead spot. The bugs are likely to be most active where there is still healthy lawn to be consumed.
3. Work one end of your can down into the soil through the grass as far as you can. It’s important to get a good seal so that the can will hold water during the test.
4. Fill the can with water. It’s a good idea to keep your hose handy in case you need to add more liquid. Any chinch bugs trapped inside the can will float to the top. Look for very tiny bugs. The nymphs are especially hard to see, but even the adults are less than ¼ inch long.
Now that you know what your problem is, it’s easy to get rid of them. Marshall Grain’s recommended organic solution is to treat your lawn with PermaGuard, which is 100% organic diatomaceous earth (DE) with pyrethrin.
Lightly dust your lawn with the PermaGuard — about 5lb per 1,000 square feet is all you need. You can cast it out by hand or gently shake it out of the bag as you walk your lawn area. The pyrethrin works quickly to kill insects on contact while the DE will keep on working until it washes away.
The brown spots are probably dead, so the grass will need to grow in from the healthy areas. Depending on how badly damaged your lawn is, it could take some time to recover, so have patience. You can speed up the recovery process by replanting the dead areas with grass plugs, or by laying fresh sod, however, these will also take some time to become established.
Eventually your lawn should recover and reestablish itself in the areas the chinch bugs have left bare and you can go back to enjoying a nice green lawn.