The population of the United States is shifting to the South and West, and if you spend a winter up north in the cold, then you’ll understand at least one of the reasons why.
At the same time that people are moving to warmer climates, the climate itself is warming everywhere. That means humans aren’t the only living things that are migrating: As warmer weather moves north, certain turfgrass insects and diseases are also creeping into newly hospitable territories. And as golf courses change their turfgrass varieties in response to warmer temperatures, they’re also inviting in new pests to once-unfamiliar regions.
In short, whether it’s due to climate or other factors, there’s a lot of movement going on out there.
Michael Bostian, superintendent at Waverly Woods Golf Course in Marriottsville, Maryland, and president of the Mid-Atlantic Association of Golf Course Superintendents, says that superintendents in that region have increasingly been battling green Kyllinga, a sedge that is native to Asia. It spread first in southern locations in warm- season grasses, and now is moving northward in cool-season turf. “It seems to be more and more prevalent here in the last couple of years,” he says.
According to the North Carolina State University Extension, “Green Kyllinga and false green Kyllinga are both perennials that tend to thrive under close mowing (inch or less) and are very prolific in areas that are poorly drained or frequently wet. Green Kyllinga is very difficult to control once the large mats tend to form.” While there are a number of control products for this weed in warm-season grasses, there are fewer options for superintendents working with cool-season grasses.
According to a recent report from Dr. James Murphy at Rutgers University in New Brunswick, New Jersey, “Preemergence (crabgrass) herbicides will not control established mats of Kyllinga. And there currently isn’t a commercially available postemergence herbicide that will provide excellent control of false green Kyllinga in cool-season turfgrass.” Research at Rutgers has found that multiple applications of halosulfuron- methyl and imazosulfuron can be effective for controlling Kyllinga.
Bostian says that while Kyllinga’s northern migration is a concern, one of the biggest pest challenges in that part of the country in recent years – the annual bluegrass weevil – has actually been moving in the other direction.
“We didn’t typically have those in this region,” Bostian says. “It used to be more of a New York and Pennsylvania pest, but now it’s coming down our way.” He adds that they’ve been present on his golf course for the past six years or so, and he’s been actively treating them for the last three years. “When we would see it in the past, we sort of let it go because it was dinging up the Poa, but the populations grew, and we started having too much turf damage,” he says.
Treatment for annual bluegrass weevil starts with good scouting, he states, noting that the recommended product solution in that area is typically either chlorpyrifos (Dow AgroScience’s Dursban) or bifenthrin (FMC’s Talstar) for adults early in the spring. “Then you go after the larvae, usually within two to three weeks, and for that superintendents are using anything from Ference (Syngenta) to Conserve to MatchPoint (both from Dow AgroSciences),” Bostian says.
In coming years, there could be an increase in traditionally southern pests in the transition zone, as more courses there seem to be “experimenting with Bermudagrass and warm-season grasses, to varying degrees of success, depending on how cold it gets in the winter,” Bostian says. Naturally, introducing warm-season grasses will eventually mean the presence of warm-season turf pests.
Dr. Nathan Walker, professor in the department of entomology and plant pathology at Oklahoma State University in Stillwater, says that’s exactly what’s happening there. “More golf courses in this area are renovating their bentgrass greens to ultradwarf Bermudagrass, and of course that means there will be new problems on those grasses that they didn’t have on bentgrass, such as root decline, root-knot nematode and leaf spot,” Walker explains.
With warming temperatures prompting courses to change to warm-season grasses, there is a learning curve for superintendents in managing these new turf challenges. There’s a bit of a silver lining, however: Warming temperatures have actually led to the decrease in the severity of one turfgrass problem on golf courses in that area. “Spring dead spot seems to be declining in importance because we haven’t had the cold winters,” Walker says.
He cautions against attributing the presence of a particular turf insect just to warmer temperatures. “Insect problems are so sporadic. You can go a couple of years without having a problem, and then all of a sudden you have a problem. That may or may not be related to warming weather,” he explains.
Still, changing temperatures can move insects around. One potential problem that could result from warming temperatures is the northern migration of fire ants – definitely not something that superintendents would welcome seeing on their courses.
Addison Barden, agronomist with the USGA Green Section, works with superintendents along the East Coast from Virginia to Maine. He says he hasn’t seen a huge pest pressure moving northward that would echo changes in climate and temperature. However, there do seem to be a few that are creeping, he states. In the lower extremities of his territory, Barden’s heard reports of some courses seeing mole crickets move from southern climates northward into the transition zone.
“There’s also some weed pressure moving north, including some different sedges,” he says, adding that there aren’t a huge number of options available for controlling some of them. “Dismiss (FMC) has been the go-to product for the sedges. Celero (Nufarm), a newer product, is also being used,” Barden says.
Lane Tredway, technical representative with Syngenta, covers a territory from Florida to Virginia. He, too, is a bit skeptical of attributing changes in the distribution of turf pests just to changes in the weather. “Certainly, we’ve seen changes in the distribution of pests over the last 20 years, and climatic conditions have changed over the last 20 years, as well,” he says. “But just about everything else about how turf has managed has changed, too. There are different grasses, different management practices. Superintendents are topdressing and using soil surfactants more. Everything has changed.”
The bottom line, he emphasizes, is that it can be difficult to say definitively why any given turf pest may be spreading its range: “In reality, it’s probably a combination of different factors,” he says.
There are, however, a couple of turf insects that Tredway says are definitely spreading northward – mole crickets and Bermudagrass mites. “They seem to be creeping their way a little bit farther north of where they were maybe 15 or 20 years ago,” he observes.
Weeds are on the move, too
On the weed front, Tredway says that doveweed seems to be becoming a more consistent problem farther into the transition zone, which could be partly due to warmer temperatures and partly due to the decrease in use of MSMA herbicides over the last 10 years. “Doveweed is a difficult weed to control. There’s really no silver bullet; it requires a combination of preemergent herbicides and postemergent products later in the season,” Tredway says.
Another thing that’s creeping northward is Bermudagrass. While it may seem that warmer temperatures will help that grass thrive in locations north of where it has traditionally been used, Tredway points out that the changing weather patterns also include more extremes. In addition to generally warmer temperatures, many locations are seeing higher highs and lower lows.
“With take-all root rot (Syngenta’s management solutions for this include Briskway and Headway), for example, some of the issues that we’re seeing on Bermudagrass greens are actually more problematic because it’s too warm in the fall and in the early spring, when light levels are too low to promote optimal Bermudagrass growth. That causes a lot of stress on that Bermudagrass plant.”
While there may be enough light to keep the Bermudagrass growing in southern areas during these periods, further north where Bermudagrass is now occasionally being installed – where there are more clouds and shorter days in the spring and fall – it would be better to just have the grass go dormant. But the unusual and increasingly common periods of heat keep it growing in a stressful environment.
That’s just one example of how it can be difficult to control diseases and insects when they appear in new places at new times. Control-product manufacturers and university researchers have to rethink their traditional recommendations, Tredway points out. In other words, what has worked in the south in the past may have to be adjusted in order to work further north.
Even as the climate continues to change, Tredway doesn’t expect to see dramatic changes in the distribution of turf pests. But gradually changing climates will cause pests to continue to move and migrate over time. And, perhaps more challenging from a management perspective, extreme temperature patterns – higher highs and lower lows – will lead to an increased incidence of pest problems popping up.
“What that’s doing is enhancing a lot of our stress-related diseases. On the cool-season grasses, we are seeing more problems with diseases like anthracnose and Pythium root rot,” he says. “On warm-season grasses, we have more significant issues with take-all root rot and spring dead spot.”
Nematodes have become a bigger challenge across the board for both cool- and warm-season grasses. “I think that comes back to the increase in abiotic stresses that we’re seeing due to extreme weather conditions,” Tredway says.