Chinchbugs

With the arrival of hot weather, the possibility of chinch bugs in St. Augustine grass is ever present. Plan now to control these pests before large, dead areas appear in your lawn.

Not all brown grass is a result of chinch bugs. Determine if your St. Augustine grass is infested with chinch bugs before applying control chemicals.

There are two ways to find chinch bugs. When they are present in sufficient numbers to cause yellowing and browning, they can be found by parting the grass at the margin of the injured areas and closely examining the thatch and base of the grass. The bugs may be seen crawling over the grass and in heavy infestations can be seen crawling over sidewalks. The immature chinch bugs are about the size of a pinhead and are bright red with a white band across the back. Adult bugs are 1/5" long, dark brown to black in color and have white wings. If you find a bug and are not sure that it is a chinch bug, mash it between your thumb and forefinger and smell it. If it has the typical stink bug odor, it is most probably a chinch bug.

If you can't see chinch bugs by examining the grass, try the coffee can technique. To do this, cut both ends out of a coffee or similar size can and sink the can 2 to 3 inches into the soil at the edge of the yellowish area of grass. Then fill the can full of water. If chinch bugs are present, they will float to the top of the standing water in a few minutes.

When testing for chinch bugs, don't be satisfied by just testing in one place. Try the test in several locations, provided you don't find them on your first attempt. A mistake most often made by gardeners in testing for chinch bugs is that they test in areas where the grass is already brown or dead. Chinch bugs have already feasted on such grass and have headed for greener pastures. Therefore, make your test in green grass adjacent to the brown areas. The can should be sunk in green grass approximately 10-12" from the dead or brown St. Augustine grass.

Two tips which make testing easier are: 1) water the lawn a day before trying to sink the can, it's much easier to get it into damp soil and 2) place a board across the top of the can and drive the can into the sod by hitting the board. Hitting the edge of the can with a hammer only bends the rim, particularly on hard, dry soil.

Cultural controls for chinch bugs include reducing the amount of water-soluble nitrogen fertilizer used, mowing at the recommended height (three to four inches) and minimizing thatch buildup. Prolonged drought stress can encourage chinch bugs. If the edges of the grass leaves start curling and appear to have a dull bluish gray color, water the lawn as soon as possible with 3/4" of water.

If 20-25 chinch bugs per square feet are detected, an insecticide application may be necessary. Spot treat when infestations are first noticed and damage is minimal. However, the entire area should be treated if the damage is widespread. For recommendations on selection and application of appropriate insecticides, contact the cooperative extension service in your county.