Chinch bugs (Blissus insularis) are an all too common pest in St. Augustinegrass. They are found on many kinds of turfgrass, but St. Augustinegrass is their favorite. You have heard of them, but do you think you would recognize one? The adult chinch bug is between 1/8-1/10 of an inch long. Pretty small, huh? They are black with white wings that each have a characteristic triangular black mark:
Chinch bug populations are typically clumped in certain areas in a lawn. Often they will start in stressed turf and are often seen along sidewalks, patios, and driveways where drought stress is more common. The insect has piercing-sucking mouthparts that they use to pierce the leafblade and extract vital plant fluids. Once the damage is done and one area is brown and dead, they will keep moving on to neighboring areas in the turf.
Proper lawn care can prevent or minimize chinch bug populations from establishing themselves in your lawn. A healthy turfgrass will be more resistant to them. This means mowing at the right height and not over-watering or over-fertilizing. The rapid lush growth that results from too much water and/or fertilizer is just what chinch bugs love to feed on.
There are also some natural predators of chinch bugs that help keep populations in check: big-eyed bugs, predatory earwigs, spiders, and a small wasp, Eumicrosoma benefica, that parasitizes chinch bug eggs. Because you want to keep these natural predators around you will need to keep pesticide applications to very specific areas and be sure to use them sparingly (always carefully following the pesticide label of course). The fact sheets linked below will indicate appropriate pesticides and if and when it may be necessary to use them. Pay attention to the part about chinch bugs becoming immune to pesticides. This is just one more reason to use them as seldom as possible.
If you suspect chinch bugs in your lawn you can bring a sample to us here at Extension and we can see if they are present. Be sure to bring a large sample, about 8″-10” square of your turfgrass that includes a progression of healthy green grass to brown damaged/dead grass. The following fact sheet explains a method by which you may check for chinch bugs in your own lawn: