There is no doubt that if a lawn turns ugly, it usually happens during the summer. As if grubs, disease, and drought stress isn’t bad enough, you also have two more foes to worry about. These pests are grouped into a category of lawn insects called “Surface-Feeding Insects”. Sod Webworms and Chinch Bugs can damage a lawn so badly that many areas cannot recover. Most lawn owners and even some professionals misdiagnose this problem as drought stress, but if you know what to look for and catch it soon enough, you can solve this problem pretty easily.
Sod Webworms: These insects only damage the lawn in their larval stage. In early summer, these overwintering larvae pupate and turn into a small moth that many people see flying erratically over the lawn as they walk across it or while mowing it. These moths won’t feed on the grass, but they can breed and lay more eggs that will hatch into more larvae. A single female can lay up to 200 eggs which will hatch in 7-10 days. These larvae will feed from July through August causing major damage to lawns.
Sod webworm larval damage appears first as brown patches up to the size of your fist. In some lawns, owners will notice holes from birds searching in these area to snack on these worms. Because it appears close to drought damage, sod webworm damage often goes unnoticed in drought conditions. The larvae chew off grass blades just above the crown of the grass plant. These small fist-size patches eventually connect, leaving a large brown, damaged area.
Finding the pest is the key. The best way to find them is to get down on your hands and knees and look closely. Look in the thatch layer for their silken tunnels and also sod webworm frass (green fecal pellets). Another trick is to apply soapy water on areas which will irritate this pest and cause them to crawl to the surface of the turfgrass. A solution of 1 gallons of water with 1 tablespoon of liquid dishwashing detergent will do the trick. Sprinkle the disclosing solution over 1 square yard of turf. If you find 10 to 15 larvae in 1 square yard of turfgrass, then treatment may be warranted. Click here to view images of sod webworm adults and larvae.
Chinch Bugs: These pests have a lot of similarities to sod webworms. They feed relatively within the same time frame, but their feeding can be extended even longer into the season if the temperatures in the fall are warmer. This overwintering females will lay over 300 eggs within a 6-8 week period. Eventually the hatched chinch bugs will begin to reproduce themselves in late summer, adding to their numbers. Like sod webworms, the damage can be difficult to differentiate between drought stress.
Chinch bugs cause significant feeding damage by sucking out plant fluids with their piercing-sucking mouth parts and also inject a toxin that causes the grass to turn yellow, then to reddish brown, and eventually dies completely. These small feeding sites begin to spread rapidly and can wipe out large areas of turfgrass.
Again, finding the pest is the key. You’ll be down on your hands and knees again for this one. Look again in the thatch layer for the insects. Pick an area right on the border of the browning area and a healthy area. This is where most of the activity can be seen. These bugs are very hard to spot because they move quickly, are very small, and often blend in with the grass very well. Click here to see images of Chinch Bugs.
Take a large coffee can and remove both ends, and plant it a couple inches into the soil. Fill about 75% of it with water. Be sure to reach down and stir the grass at the bottom as to dislodge insects clinging to the grass. Over the following 10 minutes, count the number of chinch bugs that float to the top. Be sure not to confuse them with the beneficial big-eyed bug. If the water drains into the soil too much before the 10 minutes are up, keep adding water. If you find 20 to 30 chinch bugs within that can area, treatment is advised.
Luckily, treatment and recommendations for chinch bugs and sod webworms are very similar. Most insecticides that control one will also work on the other so you won’t need to address it with 2 materials. Some of these materials work systemically as well as on contact which means if insects aren’t present at the time of application, they will be controlled as they feed on treated turfgrass. These materials may only remain in the plant for approximately 30 days, so a repeat application may be needed. A good lawn care program will include these materials as a preventative treatment to keep the populations from getting to big.
There are also other considerations to be considered. Reducing thatch layers by aerating and correcting soil pH will reduce the likelihood of problems with these insects. There are also some varieties of turfgrass that will perform better in your lawn against this pest. If your lawn is continually plagued with these pests, talk to a Certified Turfgrass Professional about additional recommendations.
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