Pests and disease decimate golf courses and can wreak havoc on a season before it even gets started. Superintendents appreciate the importance of planning and being alert to potential problems before they become season-ending catastrophes. We asked the experts about the potential pest pitfalls turf managers may face in their respective regions this year and what to keep an eye out for before it becomes a major problem.
Patrick Gross is based in Santa Ana, Calif., where he serves as the West Regional Director for the USGA Greens Section. Gross notes there is no single particularly troublesome disease or pest in the West. He attributes this agronomic status quo to the professionalism of the superintendents he works with day in and day out. “There’s not one biggie wiping everybody out [in the region],” he says. “Superintendents are on top of their game.”
Many superintendents maintaining turf in the West will be watching for rapid blight, a disease that was first identified in California in 1995, Gross says. This pathogen affects cool-season grasses and tends to thrive in soil with elevated salt content or areas irrigated with saline water. Most concerned are superintendents managing Poa annua greens, but rapid blight can also impact bentgrass putting surfaces. Its impact is devastating to turf. Rapid blight can kill infected turf in as little as two or three days. “It comes on so suddenly,” Gross says. “And it can cause a lot of damage.”
Gross recommends attacking rapid blight with a combination of Mancozeb fungicides and Insignia. A big key toward warding off rapid blight is managing soil salinity. “(Rapid blight) is very tightly related to elevated salinity in the soil,” he says. “No. 1, you’ve got to lower the salinity.”
Winter rains, or the lack of them, has a significant impact on soil’s salinity level. “Last year (the winter of 2017) we had decent winter rainfall that really leached the salt out of the soil,” Gross says. “But previous to that we weren’t getting winter rainfall and that salinity accumulates. Guys think that because it’s cool outside that they don’t have to worry about the salinity, but you should constantly monitor the salinity with a hand-held meter. So that’s important, along with leaching or heavy applications of water to drench the soil and lower the salinity.”
By now, the golf season in Florida and the rest of the Southeast has kicked into high gear. At the same time, Dr. Adam Dale has focused his attention on the Bermudagrass mite. “I got the most calls about this pest at the beginning of 2017 and probably 2016 also,” says Dale, a University of Florida assistant professor of entomology and nematology.
The Bermudagrass mite is an eriophyid mite, meaning it feasts on a single strain of turf. In this case, it sets it tastes on Bermudagrass. As is the case with other eriophyid mites, it is extremely small and extremely difficult to detect, even with a high-quality hand lens. The pest typically makes its appearance in the spring, Dales says, and is found across the Southeast, where Bermudagrass prevails.
“It is pretty widely distributed throughout the Southeastern U.S., but seems to be most problematic in Florida, Georgia, and parts of South Carolina,” he says. “But they find it over in Texas, also.”
The pest creates what Dale describes as a “witch’s broom” effect. “Imagine a chute of Bermudagrass that looks like a broom,” he says. “It’s got a long chute and all the foliage is tightly grown in a big tight wad at the tip of that chute.”
The presence of the Bermudagrass mite results in thin strands of turf that are, in Dale’s words, “really clumpy looking.” The net result is an uneven playing surface.
The pest is most commonly found on Bermuda fairways, particularly in low-cut areas. It is also found on tees and greens. To control and manage Bermudagrass mites, Dale recommends a lower mowing height than normal. “We did a trial where we had some Bermudagrass that was mowed at about an inch,” he says. “We came in and mowed it to about a quarter-of-an-inch and collected all those clippings that we cut up and removed them from the system.
“What we saw was that just from mowing really low and collecting all the clippings we reduced the damage and the abundance of the mites by about 50 percent for the rest of year.”
The nematicide Divanem has been effective in combating the Bermudagrass mite, Dale says, adding the label has recently been updated for use against Bermudagrass mites on golf courses. Dale and his team made two applications of Divanem at a 14-day interval. The most effective application rate proved to be .14 oz/1,000 square feet
For superintendents based in the Northeast, the annual bluegrass weevil (ABW) is always a concern. While the pest has been migrating westward and southward in recent years, it is most common in the Mid-Atlantic and Northeast sections of the country, as well as in Canada. It was first identified in Connecticut in the early 1930s.
Some turf experts, among them Dr. Albrecht Koppenhofer at Rutgers University and Dr. Ben McGraw at Penn State, have theorized there is a strain of ABW that thrives in a golf course environment.
The ABW is most common in the Mid-Atlantic and Northeast.”-
Jim Skorulski, a USGA agronomist based in Palmer, Mass., advocates an integrated approach in dealing with ABW that encourages establishment and growth of bentgrass, which is a less effective host. He also recommends properly timed insecticide applications – monitoring ABW activity via WeevilTrak – for maximum control of both adults and larva. This is coupled with rotating products from different insecticide groups, or those with different modes of action, to prevent or slow the onset of resistance.
With ABW, resistance issues have become more problematic in the case of ABW. “Resistance to the insecticides has been a major concern that has impacted management programs,” Skorulski says. “Researchers have demonstrated cross resistance, where the annual bluegrass weevil becomes resistant to one chemistry and is able to detoxify other chemistries, as well. Golf courses with reported resistance rely on newer chemistries that more aggressively target the larval stages of the insect.”
Skorulski notes that Ference, a Syngenta product, and Conserve, which is produced by Dow, are two of the newer products that have become popular in ABW management programs. However, in some circumstances, superintendents might benefit from tolerating some insect activity, he says.
“Control expectations can be very high, and it might not be such a bad thing to tolerate a small amount of feeding injury of annual bluegrass at least on tees and lesser-played fairway areas,” he says. “The amount of damage that can be tolerated is based on many factors and would vary from golf course to golf course. Maybe it is time to selectively reduce some of the inputs that protect annual bluegrass in favor of more durable bentgrass.”
Come spring, turf pros in the Central region will be on the lookout for dollar spot. However, “cleaning up” in the fall can reduce the likelihood of a major spring outbreak, says Dr. Paul Koch, an assistant professor of plant pathology at the University of Wisconsin. “If you go into the winter with disease, you’re more likely to have disease the following spring,” he says. “Failing to clean up areas of dollar sport or whatever it might be is going to make you more susceptible to disease the following year.
“If you cleaned up pretty well the previous year and had healthy turf growing into the snow cover, then you’ll start off the next year disease free; that puts you in a more advantageous spot. Once you get behind once there is already a disease present, it takes more effort, it takes more fungicide, it takes more money to get it under control.”
Koch has been seeing major fall outbreaks of dollar spot in recent years. Controlling the problem before snow arrives is a major challenge. “We’re seeing more and more dollar spot occur in the fall,” he says. “I don’t know why that is. There might be different genetic strains that occur in the fall than those that occur in the summer, (but) in most years we have a fairly big fall dollar spot outbreak. If we don’t clean that up before winter comes along, sometimes it’s just too late in the fall (to prevent problems in the spring). We’ve had dollar spot outbreaks in November in the past. That’s tough to clean up prior to snow cover.”
The weather also has a “trigger effect” on dollar spot that remains from the fall. Koch recalls the spring of 2012 when March temperatures in Wisconsin rose to record levels and remained there for a full week. “We didn’t see any dollar spot then,” he says. “But when it did occur in May, it was much more aggressive than it would have been in a typical year. It kind of exploded on you. Whereas, in a normal year it would be a spot here, a spot over there, it would slowly build up. That year – I think it was May of 2012 – it was very aggressive. It came on very quickly.”
What is likely happening is the dollar spot fungus is getting inside the plant well before turf managers see symptoms, Koch says. “It kind of hangs out there for a while and then there is some sort of trigger that causes symptoms to develop.”
Koch recommends combining iron sulfate with conventional fungicide applications to enhanced dollar spot control. “Iron sulfate without any fungicides, is not likely to give very effective dollar spot control,” he says, “but what it does do is when you combine it with your normal fungicide program, it helps to knock down the fungal population and makes it easier to control.”