Chinch Bugs Are No Cinch!
Nathan Riggs, Extension Agent - Integrated Pest Management
Texas Cooperative Extension, Bexar County
Summer is here and that means hot, dry conditions in the San Antonio area. With summertime conditions in St. Augustine lawns comes a common summer visitor: the Southern Chinch Bug.
The Southern Chinch Bug (Blissus insularis Barber) is nearly 3/16 of an inch long with a narrow black body and frosty white wings. Immature
chinch bugs are red or orange and do not have wings. It takes a chinch bug approximately 6 weeks or longer to develop from egg to adult,
depending on temperature. Higher temperatures will shorten this developmental time (Photo at left by B. Drees).
Chinch bugs feed primarily on St. Augustine grasses with bermuda, centipede, and zoysia grasses also in their list of favorites. Chinch bugs damage the grass by sucking sap from the grass near the base of the plant. Signs of damage on the grass are yellowing, wilting, thinning, and slowly expanding affected areas. Chinch bugs feed in large groups, or aggregations. This accounts for the expansion of damage in a radiating area away from the initial infestation. Chinch bugs usually attack grass that is in the sunniest areas of the lawn. They are not usually found feeding on grasses in the shade. One way to test for chinch bugs is to obtain a sturdy can with both ends removed. Push one end of the can into the ground at the edge of an affected area so that there is healthy grass and unhealthy grass inside of the can. Fill the can half full of soapy water. Chinch bugs will float upward in the water. If you see chinch bugs, they can be successfully spot treated with some sort of liquid insecticide that lists chinch bugs on its label. Treatment of the entire lawn is not always necessary because the chinch bugs feed in groups. Be sure the lawn does not contain high amounts of thatch. Excessive thatch can provide perfect conditions for chinch bugs to develop. Under- or over watering can also stress the grass and make it vulnerable to chinch bugs. Water enough to wet the soil to a depth of 6 inches and allow it to dry between waterings. In San Antonio, deep lawn watering once every 7 days should accomplish this.
A few words of caution: there are other conditions in the lawn that resemble chinch bug damage. White grubs will eat the roots of the grass, causing brown areas (if your dead grass rolls up like a carpet, it has been attacked by white grubs). Reflections of sunlight from windows onto the grass can cause brown patches where the grass is burned from overheating. Fungal diseases like Brown Patch and Take-All Patch can also cause similar symptoms. If you cannot find chinch bugs in your unhealthy grass, take a sample to your local nursery or the Extension Office for further examination. The Bexar County Extension Office is located at 3355 Cherry Ridge Dr., Suite 212 in Conroy Square and can be reached at (210) 467-6575.
Literature References:
Drees, B. and Jackman, J., A Field Guide to Common Texas Insects. Gulf Publishing Company, Houston, Texas, 1998.
Merchant, M. and Crocker, R., Chinch Bugs in St. Augustine Lawns. Texas Agricultural Extension Service Publication L-1766, March 1998. (PDF File)
Last updated: October 6, 2009