Overcoming the inevitable

Forecasting 2017 disease and pest problems that might affect turfgrass is a less than exact science, but turf researchers and industry insiders provide their most well-educated outlooks on what may be brewing in the coming year. And a lot will have to do with environmental conditions.

For example, fungal pathogens can build inoculum in the soil and the plant, but that really does not mean much if the conditions are not right for disease, says Dr. James Kerns, turfgrass pathologist for North Carolina State University. However, if the conditions are right, then disease pressure could be bad again.

“It seemed like the Midwest (Indiana, Ohio, southern Michigan and Kentucky) struggled with pythium root rot and root knot nematode problems,” Kerns says. “Arkansas and the central states also struggled when all the rain was falling.”

The type and severity of this year’s disease and pest issues ultimately depends on rainfall. “But, based on the weather conditions in the northern states, it seems likely that snow mold will be a problem, and there is potential damage from ice and other winter conditions as well,” Kerns adds.

Forecasting disease and pest issues in 2017 is like predicting today who will win in Week 8 of the 2017 NFL season, says Dr. Lane Tredway, Syngenta senior technical representative. It depends on multiple unforeseen factors – who’s healthy; who’s hurt; and who the teams have gained or lost in free agency. Similarly, turf pests are most strongly influenced by the current weather conditions. “Which pests become major issues in 2017 depends on what the weather does in 2017,” he says.

Long-range forecasts predict a drier fall and winter compared to last year for much of the Southeast, and so far, this is holding true. “This should be good for the health of warm-season grasses, which suffered from heavy disease pressure last winter,” Tredway says. “Superintendents should still stay vigilant for wet conditions that are conducive to leaf spot, pythium blight and rhizoctonia diseases and treat preventatively as needed.”

One exception is superintendents whose creeping bentgrass greens in the Transition Zone suffered turf loss due to persistent heat during the summer of 2016. “Any bentgrass re-established from seed or sod will tend to be more susceptible to summer diseases and abiotic stresses next year, especially if 2017 is a hot and humid summer,” Tredway says. “In this respect, hot and humid summers can have a compounding effect on the health and quality of creeping bentgrass.”

Most superintendents are aware of, or have experienced, summer bentgrass decline. Some mistakenly consider this is an outdated or invalid concept. But Tredway disagrees and uses the summer of 2016 as evidence. “When creeping bentgrass is stressed from persistent heat, humidity and mechanical stresses, it becomes more susceptible to a range of diseases such as summer patch, pythium root rot, anthracnose, algae and bacteria,” he says. “The abiotic stresses (heat, humidity, mechanical wear) are the primary issue, the pathogens are just taking advantage of the situation.”

Bermudagrass putting greens are prone to Bermudagrass decline. Abiotic stresses, specifically cool, cloudy and wet weather, cause the turf to be susceptible to a range of pathogens, such as leaf spot, pythium blight, take-all root rot, rhizoctonia zeae, cream leaf blight and other issues.

“With 2017 looking like another drought year, moisture stress on fairways and roughs is likely to cause the greatest turf losses in total area of managed turf,” says Dr. Larry Stowell at PACE Turf in California. “Poa greens will likely be plagued with heat, soil-salt and drought stress, so anthracnose and rapid blight are the most common problems we may face.”

All the major diseases will be prevalent this year, says Dr. Brian Aynardi, a Northeast research scientist for PBI-Gordon. And there is potential damage to Poa annua (even bentgrass) depending on the length of snow cover in New England, and freezing and thawing (usually 45 to 60 days of slushy snow cover with freezing and thawing will injure Poa, for bentgrass around 75 days).

“We are likely to see lots of snow mold (there has already been significant snow on the ground in the New England), and with snow freezing, thawing and melting, pink snow mold will be problematic,” Aynardi. “Gray snow mold will be big problem, as well.”

Microdochium patch (microdochium nivale) will be “a significant problem” on annual bluegrass putting greens in the costal Pacific Northwest, says Dr. Alec Kowalewski, an Oregon State University turfgrass specialist. “The fall of 2016 was very wet (lots of rain in October and November), which has produced a lot of fall disease pressure,” he adds. “This is very concerning because the peak of disease pressure typically in the coastal Pacific Northwest is in the later winter, early spring months. If we have cool, wet weather through the winter and early spring, without significant amounts of freezing temperatures, this will complicate any problems.”

Rapid blight and summer patch on Midwest Poa annua greens were the biggest disease problems observed in 2016, says Pat Gross, West Region Director, USGA Green Section, and they are likely going to be an issue in 2017 if we don’t get good winter rainfall to flush salts out of the soil.

“Dr. John Kaminski at Penn State University identified a new disease this year, pythium patch, which looks a lot like summer patch,” Gross says. “We’ll be on the lookout for that one as well. Some courses reported not getting good control of summer patch with the fungicides they were using, and it might be that they were seeing pythium patch and not summer patch.”

Ongoing drought, lack of winter rainfall and hot summer temperatures will contribute to the problem. “We really depend on winter rainfall to flush salts out of the soil, so if this doesn’t happen, then the salts continue to accumulate and we can see stress earlier in the year,” Gross says.

Prolonged periods of oppressive heat and interspersed heavy rainfall during summer 2016 meant research plots in eastern North Carolina experienced pythium root rot and physiological decline that led to a decrease in root health and overall root mass. “This has been difficult to recover from, and in 2017, I’m expecting a sensitive cool-season turf stand that will have increased vulnerability to heat/drought stress, as well as additional root disease such as pythium and take-all patch,” says Dr. Jeff Atkinson, SePRO’s portfolio leader/turf and landscape.

“On the warm-season turf side, the lingering warm temps we experienced into December in his region (60 degrees soil temperature average on Dec. 1) allowed the infection period of root damaging pathogens to continue, as well,” Atkinson says. This prolonged infection period could translate to increased amounts of spring dead spot in Bermudagrass, as well as large patch in St. Augustine and zoysiagrass, he adds.

Because of the drought and heat that plagued much for the Northeast last summer, turfgrass root systems may be weaker coming into the spring than in an average year. Long-term NOAA forecasts for the Northeast indicate a wetter-than-average spring. “Excessive soil moisture may further weaken root systems by depleting soil oxygen,” says Dr. Alex Ellram in the Department of Animal and Plant Science, College of Agriculture and Technology State University of New York, Cobleskill. “A weak root system is more susceptible to infection by `patch’ type diseases, like take-all patch, necrotic ring spot, and summer patch. Pythium root dysfunction may also be more prevalent if excessively wet conditions persist this spring.”

Long-term forecasts also indicate a warmer and wetter than average Northeast next spring and summer. These conditions promote a wide range of turf diseases, including summer patch, necrotic ring spot, pythium blight, brown patch and Waitea patch, Ellram says. Bacterial wilt also thrives under these conditions.

“Dollar spot thrives under a wide range of conditions and will likely be active most of the golfing season, as usual,” Ellram adds.

As if concerns over the usual suspects aren’t enough to keep superintendents up at night in the Southeast, Dr. Bruce Martin at the Clemson University Pee Dee Research and Education Center notes the Southeast has experienced three consecutive years with abundant moisture sometime during the fall, winter or spring.

“The worst-case scenario occurred in 2015 when we had very wet conditions in October (record flooding) and cloudy wet and warm weather that persisted into the winter,” Martin says. “Some greens were killed outright from pythium blight or take all root rot. This year we had Hurricane Matthew that could have set us up for a disaster if the weather had continued to be cloudy and wet. The hurricane was bad enough but it so far has been relatively dry and sunny afterwards. Of course, this could all change, so superintendents are wise to understand the potential pressures if conditions change.”

While Pythium and take-all root rot are not unknown diseases in Bermudagrass, the outbreaks Martin observed in 2015 were unprecedented. “For bentgrass, the challenge continues to be managing bentgrass in heat stress environments,” he says. “It is undeniable that summers are hotter than usual since we have broken heat records at least three times in the past decade. That pressure increases the challenge of managing bentgrass in this region. Pythium root rots remain the primary group of diseases that compromise bentgrass in summer and should be a major focus for managers.”

For bentgrass, obvious signs of fungal mycelium or a poor or mottled dew pattern in the morning might portend impending trouble, Martin says. For Bermudagrass, warning signs are much the same, as well as spotting non-uniform color changes in the turf canopy.

John Torsiello is a Torrington, Conn.-based golf writer and frequent GCI contributor.