Cinch bugs destroy St. Augustine grass

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On May 29, I was alerted by Scott Davis, the horticulturist in charge of the landscape at Georgia Health Sciences University, that a field of brown top millet on the campus was eaten by chinch bugs. He also saw a St. Augustine lawn that was infested. A couple days later, a fellow member of the Augusta Exchange Club told me much of his St. Augustine had died, but the centipede mixed in with it was fine. That can be a sure sign of chinch bugs.

Many people have St. Augustine grass in shady areas because it is our most shade-tolerant grass. In these areas, you don’t have to worry about chinch bugs. They like open, sunny (hot) areas of the lawn.

The first sign of chinch bug damage to a St. Augustine lawn is the grass will look wilted even though you have recently watered or it has rained. From this wilting stage it will turn yellow, then straw-colored brown. If it reaches this point it is dead.

Synthetic pyrethroid insecticides are effective in control of chinch bugs, but they don’t provide residual control and there is evidence resistance has surfaced for bifenthrin (Ortho Max Bug-B-Gon, Over ’n Out and Hi-Yield Bug Blaster). This makes one expect this has or will happen with other pyrethrins as well. All the synthetic pyrethroid insecticides end in “thrin.” These others include cyfluthrin (Bayer Advanced) and lamda-cyhalothrin (Spectracide). The Bayer Product Complete Insect Killer has a combination of b-cyfluthrin and imidacloprid so it provides a longer residual control. You can also apply Sevin but it does not work that well.

In most cases, irrigate the grass area several hours to a day prior to the insecticide application unless noted otherwise on the product label. Granules can be used but they must be watered in thoroughly. When spraying an insecticide, use lots of water (4 to 5 gallons per 1,000 square feet) to get the chemical down to the insects.

The following cultural practices can help in chinch bug control. Use little nitrogen during the hot summer months and use slow-release fertilizers. Overfertilization with nitrogen can make chinch bugs worse. Water deeply once or twice per week, applying three-quarters to one inch of water each time. Water between midnight and 10 a.m. If the thatch layer is thicker than 1 inch, dethatch the lawn as soon as possible. Topdressing is the best way to dethatch a St. Augustine lawn in order to prevent damage to the grass from a dethatching machine.

Chinch bugs can kill a lawn quickly, so if you are seeing problems, don’t delay in scouting and treating your lawn.

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