This plan allows you to get the black turfgrass ataenuis before it gets your turf
Wendy Gelernter can remember the old days when the black turfgrass ataenius (BTA) was a difficult problem and there were no real good and residual control alternatives. Now there are good insecticides available, but she cautions that life can look pretty grim even nowadays for a turfgrass manager if they don’t keep an eye out for this pest.
The Ataenius beetles, top, are blacker than the related Aphodius beetles on the bottom, and do not have hind leg ornamentation.
“It’s a pretty cosmopolitan pest. It occurs anywhere people are growing turf,” says Gelernter, an entomologist and co-owner of PACE Turf in San Diego, Calif., with husband Larry Stowell. In their consulting business they still deal with the BTA occasionally, but now there are good monitoring methods, as well as cultural and chemical treatments, that can minimize the insect’s ability to damage turfgrass. The first step is to distinguish it from the many other grub insects out there.
Root-eating larvae
The BTA is a scarab beetle, in the same group as other turf pests such as the chafers and Japanese beetle. The adult is small, less than half an inch in length, and the larvae are also much smaller than other troublesome grubs. C-shaped at rest, these white grubs never get any larger than a quarter of an inch in length. They will produce two generations in the colder Midwestern states, but propagate from April through October in mild and warm climates such as Southern California.
Grass is actually not the first choice of habitat for the adult beetles, Gelernter says, but it provides excellent feeding grounds for the larvae. In the spring, adults will fly in from overwintering areas such as wooded habitats and creek bottoms. They lay eggs in the thatch/root interface of turfgrass. Adults don’t feed on grass, but larvae feed on the roots and can do serious damage. They will inhabit any grass, but affect mainly cool-season grasses such as bentgrass, annual bluegrass and Kentucky bluegrass, because the roots of those species are shorter and more susceptible to damage than the roots of warm-season grasses. She says that facilities near livestock operations and river bottoms may have larger populations of the adults.
How to find BTA
“When the weather warms, the adults will start flying around,” Gelernter says. In warm climates there may be a few adult BTAs wandering around throughout the year, but in cold states they don’t start to emerge until the “threat temperature” is about 65 degrees Fahrenheit – that is, when days warm up to an average of 65 degrees Fahrenheit several days in a row. This still makes them the earliest white grub species to emerge.
To limit damage from sampling, make three cuts in the turf in the shape of a capital I, and peel back the sod.
Watching for the adults walking on grass or pavement is one way to become aware that BTA is present. Another is to watch for birds and skunks digging up grubs, though often those predators dig for other reasons. A better way is to monitor the turf for grubs. If patches of grass seem wilted or brown, that can be a clue that grubs are chewing on the roots, but Gelernter doesn’t recommend waiting for damage to show up.
One method of monitoring is to use the old tried-and-true soap flush. That involves making a 1 percent solution with dish soap and water, then flushing the grass with it. This will drive adults that have been laying eggs in the thatch to the surface. A method that PACE Turf has devised to facilitate the search for grubs is to cut an “I” shape in the grass with a knife and peel back the sod in both directions. Grubs can then be counted, and the grass flaps returned to their original position with minimal damage.
Now to manage them
There are several good ways to use cultural controls to minimize BTA damage, Gelernter says, the first being to grow healthy grass. Next, keep levels of organic matter low. Avoid using organic fertilizers in areas where the ataenius is known to occur in large numbers; the adults are dung beetles attracted to the odor of organic decomposition.
One way to help decrease BTA levels is to turn off the lights at night; that especially means intense lighting, such as around tennis courts, that can attract large numbers of ataenius and other pest beetles during summer months. Gelernter also reminds clients that are growing warm-season grasses that they may never have to treat for BTA because of the resiliency of those root systems. She notes that the bentgrasses also tolerate BTA better than Poa annua does.
Once large populations of BTA infest a turfgrass facility, they will likely be there year after year, she says. And if it’s a cool-season facility, that will most likely mean that managers will end up using insecticides. “Anything that works for any grub will work for black turfgrass ataenius. In fact, they’re probably easier to kill, because of their size,” Gelernter says.
Don’t wait too long
The old standbys, which Gelernter has found to still be very effective, are imidacloprid (Merit), thiomethoxam (Meridian) and clothianidin (Arena). These will be familiar to most turfgrass managers, because they are used widely in the control of many white grubs. A newer and very effective chemistry is chlorantranilprole (Acelepryn), which lasts longer and is a reduced-risk product.
All of these chemicals should be applied as a preventative as the threat temperature reaches 65 degrees Fahrenheit, or as soon as monitoring reveals the presence of BTA. Do not wait too long, as successive generations can build to high populations and leave cool-season grasses looking patchy. All products should be watered in so that insecticides reach the level of the grubs in the soil, and unlike with other white grubs, follow-up applications may be necessary. This especially can apply to warm areas where several generations can develop.
Gelernter says that PACE did some research testing an old hypothesis: that pyrethroids can be useful in spraying adult BTA and reducing populations. She says it was found that contact chemicals like cyhalothrin (Scimitar) and deltamethrin (Deltagard) could be successful in knocking down flights of BTA, but that it was impractical in that successive flights could easily repopulate the facility the next day.
To recap, BTA can be a damaging pest, especially in areas where it is established year after year. The best treatment is to monitor aggressively, be careful in the use of organic fertilizers and intense lighting around the facility, and apply preventative chemicals early as spring temperatures rise.
Don Dale resides in Altadena, Calif., and is a frequent contributor to Turf. He has covered the green industry for more than 10 years.
