Writer: Kay Ledbetter, 806-677-5608, [email protected]
Photos: Beth Ann Luedeker, [email protected]

COLLEGE STATION – The most widely grown irrigated crop in the U.S. – turfgrass – is being threatened, and Texas A&M AgriLife is leading a project to find solutions.

Annual bluegrass, known as Poa annua, is the most troublesome weed of turf systems, according to a recent Weed Science Society of America survey, and this weed has grown to epidemic proportions, causing severe economic losses.

Texas A&M AgriLife is joining scientists across the nation to address the threat with a project, Research and Extension to Address Herbicide-Resistance Epidemic in Annual Bluegrass in Managed Turf Systems.

A team of 16 scientists across 15 universities will be involved in the four-year, $5.7 million project to limit the impact of annual bluegrass, the most troublesome weed of athletic, golf, lawn and sod turf, said Dr. Muthu Bagavathiannan, lead investigator/weed scientist with Texas A&M AgriLife Research in the Soil and Crop Sciences Department, College Station.

twelve people
Members of the research team include: (l to r) Shawn Askew, Scott McElroy, Muthu Bagavathiannan, Daniel Hathcoat, Clint Mattock, James Brosnan, Becky Grubbs, Matthew Elmore, David Ervin, George Frisvold, Jay McCurdy and Bryan Unruh. Not pictured: Travis Gannon, John Kaminski, Alec Kowalewski, Bert McCarty, Patrick McCullough and Aaron Patton.

Funding is from a Specialty Crops Research Initiative Coordinated Agricultural Project grant from the U.S. Department of Agriculture-National Institute of Food and Agriculture.

“The national-scale herbicide-resistance epidemic in annual bluegrass in managed turfgrass systems is in need of critical research and extension attention,” Bagavathiannan said.

The team’s multifaceted approach will be to characterize the distribution of herbicide-resistant populations, seek weaknesses in the weed’s seed biology and growth characteristics, and develop alternatives to herbicides to supplement current control measures, with a robust extension and education program, he said.

Known popularly as the “Green Industry” or the “Environmental Horticulture Industry,” turfgrass is about a $100 billion specialty crop industry in the U.S., with about 50 million acres of managed turf operations nationwide, according to co-investigator Dr. Becky Grubbs, Texas A&M AgriLife Extension Service turfgrass specialist, College Station.

With high genetic diversity and rapid adaptation to climates and management, this species is found in all U.S. hardiness zones, said Dr. Alec Kowalewski, associate professor at Oregon State University. Even small infestations can quickly spread throughout a turf field.

Annual bluegrass, marked by its distinct light green color with white flower heads, is not tolerated in managed turf systems because of a severe negative impact on turf quality, said Dr. Bert McCarty, Clemson University professor.

Poor tolerance of annual bluegrass to moisture and heat stress as well as stand density loss due to disease and nematode infections severely affect the recreational quality of the turf, said Dr. James Brosnan, University of Tennessee associate professor.

man on one knee inspecting turfgrass
Dr. Muthu Bagavathiannan, Texas A&M AgriLife Research weed scientist, looks for annual bluegrass seedlings at the Scotts-Miracle Gro Center for Lawn and Garden Research at Texas A&M University in College Station.

The rapid rise and movement of herbicide-resistant Poa annua from one location to another might be linked to contaminated turfgrass seed being planted or Poa-infested sod installed unbeknownst to turf managers, said Dr. Aaron Patton, Purdue University professor.

Understanding resistance mechanisms may provide insight for developing suitable management practices, said Dr. Scott McElroy, Auburn University professor. If the genetic relationships can be determined between resistant populations, suitable management practices could be identified and implemented to prevent their spread.

A common South Korean golf course practice is to clean golf shoes with compressed air after finishing a golf round. This simple practice could reduce the spread of herbicide-resistant populations across golf courses, and in turn reduce the amount of herbicide applied there and to other turfgrass areas, said Dr. Patrick McCullough, University of Georgia professor.

Dr. Travis Gannon, North Carolina State University associate professor, said the potential of non-target-site resistance (NTSR) mechanisms is a growing concern because such mechanisms may confer resistance to unrelated herbicide groups. “We are excited about the opportunity to investigate NTSR among Poa populations across the national scale.”

Virginia Tech professor Dr. Shawn Askew said because the biology and ecology of Poa has not been adequately studied, the project will investigate seed persistence in the soil seedbank, seedling-emergence patterns and phenological development to identify best management strategies.

“Stakeholders have told us a major limitation with resistance management is the lack of effective non-chemical tactics,” said Dr. Matt Elmore, Rutgers University assistant professor.

Research needs to evaluate cultural tactics such as grass species and variety selection, mowing regimes - height and frequency, grass-clipping removal at mowing, as well as irrigation and nutrient management, said Dr. Bryan Unruh, University of Florida professor. Fraze mowing, which removes the top inch of soil along with weed seeds, is another approach to be evaluated, Brosnan added.

“Socioeconomic factors, such as technology expectations and prices, play a major role in the adoption of best management practices,” said Dr. David Ervin, Portland State University professor. The project will conduct focus groups and a national survey to understand the behavior of turf managers and the factors influencing decision-making by them.

Twelve people seated around a table talking
Members of the research team met in College Station to initiate the annual bluegrass research effort.

Weed-resistance management may be expensive in the short-run, but it can pay off in the long-run, said Dr. George Frisvold, University of Arizona professor. Understanding the long-term economic implications of management practices and being proactive are imperative.

All findings from the project will be disseminated through an extensive outreach program, including field days, small-group trainings, webinars and bulletins in all the states for stakeholder interaction, said Dr. Jay McCurdy, Mississippi State University assistant professor.

The project also includes disseminating the research findings through classroom education and student training to reach the next generation of turf managers, said John Kaminski, Pennsylvania State University professor.

According to the International Survey of Herbicide Resistant Weeds, annual bluegrass ranks third among all herbicide-resistant weed species globally, with resistance to at least nine different herbicide modes of action.

One stakeholder, pointing out the seriousness of the problem, said, “We just completed our putting green renovation costing $3 million, driven largely by the fact Poa annua was the prominent grass, which created chronic ‘life support’ attention.” Another said, “Finding solutions to this problem could save homeowners, public entities, golf courses and sports complexes millions of dollars.”

With a strong clientele network in place, the team has been able to identify the needs of the industry and other stakeholders as we move forward with the research, Bagavathiannan said. And while the project will directly benefit sod farms, golf courses, athletic fields and residential turf systems, it also will improve social and environmental benefits to the general public.

For more information, please contact any member of the team: