Sample for chinch bugs
Chinch bugs rapidly kill turf once they've become established. Although they don't attack all grasses, some of the most common warm- and cool-season turfgrass species are likely chinch-bug targets. Methods to minimize the occurrence of chinch bugs exist, but once they're on the rise, you can't turn your head. Your only practical course of action to save chinch-bug-infested turf is to apply insecticides.
To find out if you have a chinch-bug problem that warrants an insecticide application, you must identify the problem, find the chinch bugs and check population levels. You can accomplish all of this by adopting the following chinch-bug-sampling plan:
* Recognize the problem - Chinch-bug damage. Chinch bugs tend to attack a plant in a group, then move on to other plants. Because they attack in groups, damage starts as small patches of brown turf. As damage worsens, patches may coalesce to form larger ones.
Chinch bugs damage turfgrass with their piercing-sucking mouthparts by injecting salivary fluid into crowns and stems and sucking out plant fluids. Their saliva may disrupt water-conducting vessels in the plant, causing it to wilt, turn yellow and then brown.
- Susceptible grasses. Chinch bugs don't attack all grasses. If you manage turf in the warmer regions, you might see them damaging various grasses, but St. Augustinegrass is their favorite host. You generally will not see them in bermudagrass, bahiagrass or zoysiagrass. In some cases, they have been such problems that turf managers have switched from St. Augustinegrass to other species, such as bahiagrass. When I hear someone describe blotchy, dead St. Augustinegrass areas, often with weeds growing in the middle and yellowish margins, I think, "chinch bugs."
In the temperate areas, chinch bugs attack the major turfgrasses, especially Kentucky bluegrass but also fescues and ryegrasses. Although a particular biotype of chinch bug usually feeds on a single turfgrass species, they also jump hosts, especially when new grasses are introduced to an area. This happened to buffalograss in the early 1990s. No grass is completely safe.
Some cool-season varieties with high endophyte content experience less chinch-bug damage. Endophytes are benign fungi that colonize the internal tissue of grasses. There have also been genetically resistant varieties of St. Augustinegrass, such as Floratam, that were unaffected by chinch bugs, but after a dozen years they too were overcome. I reported a new race of chinch bugs that can feed on the Floratam variety of St. Augustine-grass. Because of Floratam's initial resistance, some sod growers had forgotten what chinch bugs looked like. Entire sod blocks were lost before they could be treated.
* Find and identify the culprits Accurate detection also is critical because turf managers often blame chinch bugs for things they don't do, such as injury from drought, disease or even nutritional problems. Chinch bugs are small, with adults measuring 1/8 to 1/6 inch long. Thus, many people don't know what they look like. Chinch bugs run faster than other major lawn pests, such as mole crickets, grubs and lawn caterpillars. So the moment you start parting the turf to sample, the bug is "diving" for deep cover. Unless you know for what you're looking, you may not see it.
Chinch bugs seem to hide at your arrival, probably detecting the vibration of your feet. Look for the slate-black bodies of the fleeing adults (see bottom photo, page 30), with silvery wings covering most of their back (the dorsal abdomen). The pattern of the wings and their overlap across the back gives them an hourglass or "crossed-arms" pattern. Juvenile chinch bugs (see top photo, page 30) go through progressions (instars) from red to brown before finally becoming winged adults. The easiest way to picture the first instars (they are only 1 mm long) is to think of spider mites. The early instars also walk slowly, so they're not hard to find.
At least four species of chinch bugs affect turfgrass, with different hosts and geographic ranges. However, their detection and treatment is similar.
1. Determine when and where to sample Sample whenever you think chinch bugs might be damaging your turf. Realistically that will be after you actually see a small amount of damage. Also, damage is most common in temperate areas from July through September, depending on your latitude.
You won't be able to effectively sample unless you know where to check. Chinch bugs can occur in any square foot of grass. Before they start causing widespread damage, they form localized "hot spots." Finding a hot spot before it is visible, among thousands of square feet of turf, is akin to winning the lottery, unless you first know where to look.
The best place to look is in hot, dry places on your grounds. These are the conditions chinch bugs prefer and where their populations are more likely to rapidly grow. Thus, you will notice them in drier, sunnier parts of a lawn. A source of radiant heat, such as a driveway or a well-drained, sunny area, such as a south-facing hill, favors chinch-bug outbreaks. I say "outbreaks," because this describes the ability of chinch-bug populations to rise quickly from almost undetectable background numbers to lawn-killing numbers. Typically, you'll see the damage before you recognize that you have chinch bugs, but not before it's too late to treat. How do you find themand implicate them as the cause?
My experience in Florida has taught me that chinch bugs are more active in the late morning, when temperatures are rising rapidly. That's the best time to look. The yellowish area of dying turf is where chinch-bug numbers are highest and where you are more likely to find them. Walking quickly into the damaged area, you must stoop or kneel in the turf and quickly spread apart with your hands a 6-inch-diameter patch of turf. Usually, if you do this three times in a prime area and find no chinch bugs, they are not currently active and something else is damaging your turf. If I am not at first successful, I look for a 6- to 12-inch-diameter "island" of green turf, surrounded by dead grass. In the island of green, chinch bugs will be concentrated as they destroy their food supply-the surrounding turf.
2. Sample your turf You can use two common methods of detecting chinch bugs. The simpler, but less-accurate, method is to part the turfgrass with your hands and look for bugs. A somewhat better method is to float them out of the turf in an open cylinder that you have worked into the thatch and filled with water.
* Open-cylinder flotation. The open-cylinder-flotation method is more accurate than hand-parting because it forces chinch bugs up from the thatch, rather than allowing them to hide. Chinch bugs do not live under the soil, so they require nothing more than water to bring them up.
- Get a coffee can or other large metal container and cut open both ends. You also can use a commercially available sampling ring, which is safer and more efficient than the coffee can. The ring is equipped with handles and has a sharpened bottom edge, which may be scalloped or serrated. By grasping the handles and twisting the sampling ring while pushing down, you can force it through the thatch.
- Work the open can into and through the thatch. If you are using the coffee can, you will almost certainly need to use a knife to cut a circular slit through the thatch to accommodate one of the open ends. When the container is firmly sealed into the soil to a depth of about 1 inch, it will serve as a leaky reservoir.
- Pour water into the container, carefully so as not to dislodge too many leaf clippings.
- After 1 to 2 minutes you should see chinch bugs float to the surface. They try to stay under water, usually finding and becoming attached by capillary tension to an air bubble, while holding onto a grass blade. Eventually the bubble becomes large enough to pull away from the leaf and, together, bug and bubble rise to the surface.
* Sliding-foot method. Interestingly, other sampling methods exist. A Mississippi State University Extension bulletin says, "You can readily find any chinch bugs by slowly sliding your foot through the sod and watching for the bugs to crawl across your shoe." That sounds easy enough. I have also noticed the distinctive, pungent odor of chinch bugs when I mow. It's not as reliable as other methods, but it has alerted me to stop and check for the bugs.
3. Determine when to treat Some argue strongly for the need for early detection. However, integrated-turf-management workers have advised that a level of 10 to 15 adult chinch bugs per square foot is a treatment threshold. I have never seen such a high count except when chinch bugs were already damaging the turf. Thus, to prevent visible damage, you may need to use a lower treatment threshold. However, avoid treating without first verifying the presence of chinch bugs through sampling.
4. Conduct follow-up inspections After you've made your application, check back in a couple weeks. It is likely that chinch-bug activity will have ceased, but occasionally a chemical treatment will fail for some reason. Checking back is one way to validate control for your client.
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