Bug of the Day: Southern Chinch Bug
The southern chinch bug, Blissus insularis, is a tiny bug with a big appetite. Though it will attack many plant species, this bug especially loves to feed on St. Augustinegrass, which happens to be the most popular turfgrass species in Florida.
The southern chinch bug is a true bug, a member of the insect order Hemiptera. It’s a native species and feeds on plant sap, using its piercing/sucking mouthparts like a straw. (St. Augustinegrass is also a native Florida species, in case you’re wondering.)
The southern chinch bug is not a significant pest of other turfgrass species, such as centipedegrass or Zoysiagrass, though it will attack them. But with so much St. Augustinegrass in the state, each year Florida home and business owners spend millions of dollars to control chinch bug infestations and replace damaged turf. Additionally, when St. Augustinegrass dies, it opens up space and allows sunlight to strike the ground, which may promote weed growth – yet another potential expense.
An adult southern chinch bug measures about 6 millimeters in length and the adults are dark and oval-shaped, with whitish wings folded across their backs. Oddly, chinch bugs rarely fly, so you’re unlikely to see them airborne, even in areas with heavy infestations. Instead, they’ll be most abundant in the turf thatch, which is the spongy layer of roots, shoots, stems and decaying plant material that is located just below the green sprigs of live grass. The thatch extends down a few inches from the surface, and, from the bug’s perspective, it’s a great place to be.
To feed, a group of nymphs and adults will gather at the base of one sprig and work as a team, feeding until the blades of grass wither, then they move on down the stolon (the “stalk” connecting the sprigs) and begin feeding on the next sprig, until all the turf in the area has been drained of sap. This is the reason that damaged areas tend to be in a circular shape, as a result of the bugs moving from sprig to sprig, systematically.
This behavior also means that chinch bug infestations can spread from one yard to another as the bugs wander in search of fresh growth. Despite its tiny size, a southern chinch bug can walk 400 feet in less than an hour. (How close is your nearest neighbor?)
Southern chinch bugs prefer damp environments and warm weather. They aren’t typically killed off by freezing weather (well, Florida’s version of freezing weather), so southern chinch bug populations tend to decline a bit in the fall and then pick up again in the spring. The worst infestations tend to appear in the central and southern parts of the state. Peak infestations are said to occur in early July.
On a badly infested lawn, an observer might be able to see chinch bugs running up and down blades of grass in the infested areas. Otherwise, it can be difficult to recognize an infestation. Infested lawns will have patches of dead, brown grass that are roughly circular in shape, and possibly yellowed areas, too. However, these same symptoms can be caused by several conditions, so it is important to verify that you actually have a chinch bug infestation before taking further action.
The good news is, there’s a simple do-it-yourself method for detecting chinch bugs in your lawn. Cut the bottom off a metal soup can or coffee can, then get a trowel and go pick a spot just outside an area where the grass has died. Put the can down on some living and a little dead grass, then use the trowel to cut into the soil around the outside of the can. Push and twist the can into the soil until the bottom is about three inches below the surface. Next, get a jug of water or a garden hose and trickle water into the can for 5 minutes, making sure to keep an inch or two of water in the can above the grass at all times. If chinch bugs are present, specimens should float to the surface of the water – you can collect them and save for further identification at your local UF/IFAS Extension office. (LINK TO http://ifas.ufl.edu/maps) Repeat the process several times, just outside the perimeter of the dead area(s) you are concerned about.
If you believe there is a chinch bug infestation, it’s time to call in a professional lawn-care or pest-management company, because the preferred insecticides are not available over the counter to consumers. Furthermore, there have been reports of chinch bug populations developing resistance to popular insecticides, and, unlike the average homeowner, a professional should be aware of any resistant populations in your area and know how to address them effectively.
Discouraging chinch bug infestations is much easier than treating them. It’s mostly a matter of proper lawn care, although there’s no guarantee it will be 100 percent successful. Chinch bugs prefer to feed on weak, stressed grass, so if you have a St. Augustinegrass lawn, do your part to keep it strong and healthy: Adjust your mower height to leave the blades of grass 3 or 4 inches long, and have your mower blade sharpened regularly to prevent ragged cuts that delay healing. Also, avoid overuse of inorganic nitrogen fertilizer, and irrigate St. Augustinegrass only when needed – that’s when the blades begin to show signs of wilting by folding together down the middle.
You can learn more about the Southern chinch bug in this “Featured Creatures” document from the UF/IFAS Entomology and Nematology Department, http://entnemdept.ufl.edu/creatures/orn/turf/southern_chinch_bug.htm, and from this series of from the EDIS online Extension library — https://edis.ifas.ufl.edu/topic_southern_chinch_bug.
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UF/IFAS Photo by Lyle Buss