If brown, patchy dead spots begin appearing in healthy grass this summer, before reaching for the sprinkler, think again. The sun-scorched appearance may actually be the result of heavy-feeding chinch bugs with hearty appetites.
Chinch bugs are known to devour St. Augustine grass, but are also destructive to Centipede grass, Zoysia grass and Bermuda grass. When feeding, a chinch but punctures the grass stem with its needle-like mouth, sucks the juices and injects a toxic fluid that destroys the plant. As the grass dies, the sap-sucking pest proceeds to feed on surrounding healthy turf.
TELTALE SIGNS. Dead spots resulting from various turf ailments can be confused with chinch bug damage. For example, brown patch is a common disease that affects St. Augustine grass. Its symptoms include circular or semi-circular patches of dying grass. In contrast, expanding, irregular patches of dead grass surrounded by a ring of yellowing, dying grass likely indicate the presence of chinch bugs. The best way to confirm suspicions is to detect the insects in the grass.
Adult chinch bugs are very small- less than one quarter of an inch long. They have black bodies and white wings with a distinctive black triangle. Nymphs are smaller, wingless and appear reddish in color with a pale yellow band on the back of the abdomen. They can be detected by parting grass in areas just beginning to wilt and examining the turf base and ground. Another method is to cut out both ends of a large can and push one end into the yellowed grass and fill with water. If chinch bugs are present, they will float to the top. During heavy infestations, chinch bugs may also be seen on nearby sidewalks, porches or buildings.
BREAKING THE CYCLE. Adult chinch bugs become active and mate in late spring or when the temperature reaches 70 degrees Fahrenheit. Females can lay between 200 and 400 eggs over a period of three to four weeks. Hungry nymphs begin feeding immediately after hatching, and tend to cause more damage as the weather becomes warmer and drier. As chinch bugs mature, they mate and produce a second generation in the North and up to seven generations in the South.
Proper watering and fertilizing techniques, thatch control and planting resistant grass varieties are good preventative measures against chinch bugs. But when dead spots begin to show, accompanied by chinch bugs, corrective action is necessary. An insecticide labeled for chinch bug control can help eliminate these unwanted pests.
Late spring is an excellent time to apply Dursban insecticide, as it helps control adult chinch bugs before they lay eggs. Dursban can also significantly decrease chinch bug populations if an infestation is detected during the summer months. Products containing Dursban insecticide (chlorpyrifos) are available in a variety of formulations, and can be found in most lawn and garden stores and do-it yourself home centers.