Down with anthracnose

From under the radar to a starring role, anthracnose has made a major negative impact on putting greens over the last decade. Bruce Clarke, PhD at Rutgers University, has studied the rise and is working diligently to ensure there’s a fall in this turfgrass diease’s future.

“Anthracnose is a tremendous problem,” he said. “Funny, because before 2000 it wasn’t much of a problem ... an also-ran disease.”

Along with Clemson’s Bruce Martin, Clarke conducts one-day seminars on growing healthy turf. He always asks the room of superintendents to name their top disease problems. Ten years ago, anthracnose may not have even cracked the Top 10. In recent years, however, he saw it “creeping into the Top 3.”

“It moved from an insignificant problem to a major problem,” Clarke said.

Good news, though. Over the last two or three years he’s starting to see this trend reverse as many superintendents are less likely to name anthracnose as their major issue. Superintendents are no longer “bragging” about mowing below 1/10 inch. They counter with more rolling.

Clarke and researchers across the country are looking at the impact of management practices on anthracnose - chemicals, fungicides, management, breeding, etc. - but a great deal remains mystery.

According to Clarke, fungicide programs in the past haven’t worked all that well ... “we’ve had resistance” ... but on the other side of the coin, he started to see reduced resistance if used at higher rates.

He called Tourney “a good DMI,” but admitted not all DMIs are created equally. While Eagle and Bayleton were not terribly effective because they’re not as active, Tourney and Banner are active at a much lower concentration.

Finding the right DMI is one thing, but personal preference - or past experience and concerns - is another issue in the fight against this disease.

“A lot of superintendents don’t like using DMIs during hot weather,” Clarke said. “We found they can be used, but you need to be careful.”

He recommends reducing rates and tank mixing with another fungicide, like Signature. During cooler weather, there’s no problem going with higher rates.

As with most turfgrass diseases, the most severe strains of anthracnose are found around turf that is under stress or has been weakened. Currently, the majority of anthracnose is found in the Mid Atlantic, New England, Upper Midwest and even Southern California.

Research
Clarke has been working closely with Rutgers agronomist James Murphy and students Chas Schmid and James Hempfling on a three-year project funded by the USGA. In tests led by Hempfling, they have found that topdressing reduces the severity of anthracnose and looked at the effectiveness of spring and fall applications, as well as summer. Preliminary results have found that spring applications proved to be just as beneficial as summer.

Some superintendents don’t like topdressing, Clarke acknowledged. If the disease appears, will topdressing after the fact be effective? According to Clarke, it can work, but takes some time.

Next is compiling Best Management Practices such as: When do superintendents need to buy topdressing? If they apply in the spring, can they back off in the summer? And more. He expects to learn more over the next two years. Schmid is looking at the effects of nitrogen on anthracnose. It is proving very effective, but can you apply too much nitrogen? Applying as much as 3/10 lb. every week can lead to eve more anthracnose, according to the early findings.

The law of diminishing returns, Clarke said: “Too much of a good thing can hurt.”

Many superintendents are pressured to increase green speed, which is rendering turf more susceptible to disease. Clarke’s research has found you can significantly reduce anthracnose and maintain green speed by:
(1) increasing heights of cut and either
(2) increasing mowing frequency, and/or
(3) initiating frequent lightweight rolling.

Winter Damage
Following a winter that saw many areas experience record snow and ice, some superintendents are already seeing signs of anthracnose where there has been some physical damage from the weather.

Clarke admitted they don’t know a lot about the cold-weather strain, but said that, too, is being researched.

While not immediately seen, if the winter weather weakened turf - which remains weak going into warmer months - superintendents may see severe anthracnose this summer.

Advice
A great deal of Clarke’s work on anthracnose can be found online. Check out: http://www.turf.rutgers.edu/greenexpo/anthracnose.pdf

As for tips:

• Avoid mowing below 1/8 inch and roll to increase greens speeds;

• Don’t rely on a single fungicide group; and

• Don’t let greens get too lean on nitrogen or lose soil moisture.

Further assistance on battling anthracnose, as well as other turfgrass diseases, can be found courtesy Peter Cookingham, who has been compiling a turfgrass database that includes more than 175,000 records - Turfgrass Information File (TGIF) - at Michigan State. That can be found at: http://turf.lib.msu.edu/