Early to rise

Once the right weather conditions are in place, Poa annua moves quickly to seedhead development. BUGWOOD.ORG

As if golf course superintendents didn’t have enough to worry about, springtime temperatures set records across the nation. According to the National Ocean and Atmospheric Administration (NOAA), more than 15,000 daily record-high temperatures we set in March. Meteorologists used words such as “astonishing” and “amazing” to describe the phenomenon, and NOAA declared it the warmest March on record in the contiguous United States.

But before you could get the shorts and sunglasses out for good, temperatures close to normal quickly returned, along with dire weather warnings in the Midwest. Weatherman have been blasted for inaccuracy since the Babylonians used astrology to forecast temperatures in 650 B.C., but today’s climate patterns seem to make all the new technology and computer models about as accurate as reading the stars.

The warmer temperatures made Poa annua control an earlier issue than usual. “We have been relatively wet, and with the mild winter temperatures this was one of the worst Poa seasons I have seen,” says Roger Meier, CGCS, golf course superintendent at Valhalla Golf Club in Louisville, Ky.

Annual bluegrass causes several types of headaches on the golf course. The rapid seedhead development is first, and PGR (Plant Growth Regulator) sprays to control the pesky intruders must be timed with the appearance of the “boot” or seed sheath. Some superintendents use Growing Degree Days (GDD) to start their program, while others rely on weather patterns. Phenology clues, such as forsythia blooming, are also employed.

“A turfgrass plant doesn’t recognize the calendar,” says Dean Mosdell, technical manager for Syngenta. “When conditions are right, it wakes up and grows regardless what the calendar says.”

“Spring temperatures have been higher in most of the northern tier states and that translated into earlier Poa annua maturity and seed head production,” says Roger Storey, vice president of the turf and ornamental division of SePRO Corporation.

“You want to put down Embark right after the last frost,” says Kevin Hicks, superintendent at Couer d’Alene Resort Golf Course in Couer d’Alene, Idaho. “This year we sprayed on March 15, and we’re usually done around the first of May.”

With the famous “floating green,” Coeur d’Alene is a destination course, and needs to be in top condition during its relatively brief playing season. “We have seven months to make money,” says Hicks. “If I make a mistake, it affects revenue.”

The challenge lies in the large percentage of Poa annua on the course. When Hicks began working on the course nine years ago, the greens and fairways, originally seeded bentgrass, were largely Poa. “I was in a meeting this morning where the rep had a product that promised to take out the Poa,” Hicks says. “I wouldn’t have any grass left!”

A split application of Embark “carries us through the heavily seeded part of the year,” says Hicks. “Then we use a combination of Primo and Proxy for trailing seedheads.”

Application of PGRs have to be properly timed to affect Poa annua. BUGWOOD.ORG

During mid-summer, Hicks switches gears again. “We’ve been really happy with Legacy; it’s a combination product and gives us very effective long-term control.”

“Initial applications of Legacy at the lowest label rate recommendation should be started after the bentgrass is fully active,” says Storey. “After the initial application, rates can be increased to gain the desired turf growth and clipping reductions.”

Strategies to deal with Poa will vary depending on how what percentage of the turf is “infested.” Clay Stewart, superintendent at Idle Hour Country Club in Lexington, Ky., is “only looking at less than five percent on the greens and 10 percent on the fairways.” The unusual weather patterns has affected his application timing as well.

“We put our last application of Cutless down about last Halloween,” he says, “and we started up again about four weeks earlier than normal – about the first of April.”

“Under a Cutless program, it is important to continue applications through the summer months during the periods that Poa annua is stressed,” says Storey. “The most significant declines in Poa annua population are achieved by continuing the program starting in the spring and continuing through the summer and into the fall.”

Stewart sprays every two weeks with 10-13 ounces per acre of Cutless on putting greens. On fairways, approaches and tees he uses eight ounces of Cutless mixed with six ounces of Primo every three weeks. PGRs should be watered in after application.

“We vary our rates according to the weather,” Stewart says. He is on a season-long program to suppress the annual bluegrass. “We make the rates a little higher in the spring and fall and back them off in the summertime. It also depends on whether we are also spraying fungicides and which ones we are using – some have growth-regulating properties. So we’ll back off that week because you don’t want to shut everything down.”

The type of PGR and the rates and application timing will also depend on whether the goal is control or elimination. “Primo is used when maintenance is the goal,” says Mosdell. “If control or elimination is the goal, you can use stronger PGRs such as Trimmit.”

“In the Southwest, superintendents use Trimmit on bentgrass greens in early summer until it gets really hot,” says Dr. Dave Kopec, turfgrass specialist with the University of Arizona Cooperative Extension in Tucson. “At that point, the Poa retreats. Then they can pick up applications in the early fall.”

Overseeded Bermudagrass greens require a different regime. “You can uses multiple applications of Legacy, but you need to be careful when the Bermuda breaks dormancy,” Kopec cautions. “The PGR can actually slow the Bermuda down, because it’s taken in by the roots as well as the shoots.” In the summer, Poa isn’t an issue in Bermudagrass greens because the vigorous growth will choke out the invader.

Of course, the bottom line is that healthy, vigorous turf will minimize Poa infestation no matter what type of grass is grown. “As soon as we are able to control moisture and grow healthy turfgrass plants, we can combat the Poa and keep it in check,” says Meier.

“We actually have a good climate here in Kentucky for Poa control,” Stewart says. “It gets hot and dry in the summer and Poa doesn’t like that. So with the PGRs the Poa gets regulated and the bentgrass justs crawls right over the top of it.”

Even the most diligent program will not result in complete eradication. Stewart is in the fifth season of his program. “By no means do we eliminate it, but we’ve been able to significantly reduce it,” says Stewart. “Especially in our fairways – we’ve seen a significant reduction.”

The take-away message? If you are on an ongoing program for Poa managment, keep your timing on schedule. As temperatures rise, PGR rates should drop. Hot, dry conditions are Poa annua’s worst enemy. The best advice is the same as you have heard for almost every turfgrass challenge. Provide the best possible growing conditions for your turf, and you should be able to sail through the summer ahead.

Helen Stone is a Las Vegas-based freelance writer and frequent GCI contributor.