Cover Story

Success of the USDA-Funded Resist Poa Project

By J. Scott McElroy Professor, Turfgrass Management and Weed Science, Auburn University

and James D. McCurdy Professor and Extension Specialist, Turfgrass Management, Mississippi State University

Given the current climate surrounding federal funding discussions, we want to provide detailed information about research outcomes from the ResistPoa project. Our goal is transparency about what taxpayer dollars accomplished when this project received funding. For information regarding this project, please see http://resistpoa.org/

Project Background

ResistPoa launched in 2018 as a nationwide initiative to tackle the growing problem of herbicide-resistant annual bluegrass (Poa annua) in turfgrass systems. This four-year, $5.7 million project, funded by the USDA Specialty Crop Research Initiative brought together 16 scientists from 15 universities across the country.

The project had clear objectives: develop better management practices for annual bluegrass control, map the extent of herbicide resistance nationwide, and create decision-support tools for turf practitioners. Essentially, we needed to understand how bad the resistance problem really was and give golf course superintendents, sports field managers, and other turf professionals the tools to fight back.

Annual bluegrass might seem like a small problem, but it's not. This weed costs the turfgrass industry millions of dollars annually in control measures and lost playability. When herbicides stop working, managers face expensive reseeding, overseeding, and intensive maintenance schedules that strain budgets and resources.

Major Research Discoveries

Nationwide Resistance Survey

Our team's biggest accomplishment was conducting the first comprehensive national survey of herbicide resistance in annual bluegrass. We collected and tested over 1,300 populations from turf sites across five different climate zones. The results were sobering—by 2023, we documented populations resistant to up to nine different herbicide modes of action.

This wasn't just academic research. These findings gave turf managers concrete data about what to expect in their regions. Instead of guessing whether an herbicide might work, superintendents could now reference our maps and data to make informed decisions about their control programs.

Understanding Resistance Mechanisms

We dug deep into the science behind why annual bluegrass develops resistance. Through molecular analysis of dozens of populations, we identified specific genetic mutations that allow the weed to survive herbicide treatments. For example, we discovered a novel mutation in the β-tubulin gene that helps annual bluegrass resist popular pre-emergence herbicides like prodiamine.

But genetics wasn't the whole story. We also found that annual bluegrass uses other tricks—enhanced metabolism and reduced herbicide uptake—to survive treatments. These nontarget-site resistance mechanisms were particularly common with ALS-inhibiting herbicides like foramsulfuron (Revolver) and trifloxysulfuron (Monument).

Practical Management Solutions

Research is only valuable if people can use it. Our team tested alternative control methods that don't rely solely on herbicides. We demonstrated that aggressive fraise mowing (essentially shaving the turf surface) could dramatically reduce annual bluegrass infestations in bermudagrass turf. While this technique isn't suitable everywhere, it gives managers another tool in their arsenal.

We also examined how cultural practices affect the weed's competitiveness. Studies in Oregon showed that adjusting irrigation frequency and phosphorus fertilization could influence how well annual bluegrass competes with desirable grasses. These findings are being incorporated into our best management practice guidelines.

Human Factors Research

What makes ResistPoa unique is that we have included social scientists to study the human side of weed management. Through surveys and interviews with turf managers, we identified real barriers to adopting better practices: budget constraints, risk aversion, and simple lack of awareness about resistance.

We developed a user-friendly decision support tool—essentially a calculator that helps superintendents visualize the longterm benefits of diversified management versus short-term cost savings. This economic modeling helps justify upfront investments in integrated approaches rather than relying on the same herbicide year after year.

Sharing Knowledge

From day one, we emphasized getting information to the people who needed it. The project created ResistPoa.org as a central hub for resources, now hosting about 70 educational documents that users can filter by turf system and control method.

We produced a best management practices poster explaining herbicide modes of action and effective rotation strategies. This poster was distributed to over 2,000 stakeholders in print and downloaded more than 1,000 times online.

Our team organized field days, workshops, and webinars across the country. These weren't just presentations—they were hands-on demonstrations where turf managers could see control trials in action and ask questions directly.

Perhaps most importantly, we trained the next generation. At least 22 graduate students, 25 undergraduates, and roughly 10 postdoctoral researchers received training through ResistPoa. These students are now professors, consultants, and golf course managers, multiplying the project's impact.

Industry Impact

The real test of success is whether the turf industry is actually using our findings. Early indicators are positive. Golf course superintendents are referencing our resistance maps to make proactive decisions about herbicide rotations. Instead of waiting for a product to fail, they're switching to different chemistries based on what our survey showed in similar conditions.

We worked closely with industry advisory panels from the beginning, including golf course superintendent associations, sod growers, and lawn care companies. This collaboration ensured our research reflected real-world conditions and that recommendations fit industry needs.

When preliminary results showed certain populations surviving standard herbicide rates, industry partners helped us quickly alert practitioners so they could adjust rates or tankmix with other products. Seed producers worked with us to test for annual bluegrass contamination and resistance in turfgrass seed lots.

Scientific Output

The project generated over 20 peer-reviewed publications in journals like Weed Science, Crop Science, and Weed Technology. This wasn't just about meeting academic requirements— these papers ensure the knowledge is archived and accessible to guide future research and management decisions. Our management guides are “Open Access”—you can download them from the Crop, Forage & Turfgrass Management Journal.

Our investigators delivered dozens of conference presentations at weed science and turfgrass meetings, sharing results throughout the project's duration rather than waiting until the end.

Long-term Value

ResistPoa created lasting benefits beyond its four-year timeline. The network of scientists, Extension agents, and industry professionals formed during the project continues to collaborate on turf challenges. We've seen the power of coordinated research, and that collaboration model is being applied to other problems.

The students and researchers trained under ResistPoa have spread throughout the industry, carrying this knowledge into their new roles. This multiplier effect means the project's impact extends far beyond the original $5.7 million investment.

Turfgrass represents a $100 billion industry encompassing millions of acres of golf courses, sports fields, and maintained landscapes. ResistPoa demonstrated how targeted federal investment in specialty crop research can protect this industry and the green spaces Americans value.

Annual bluegrass remains a formidable opponent, but the collective action marshaled by ResistPoa has given the industry evidence-based tools to manage this weed sustainably. The project exemplified how integrated approaches—combining science, education, and industry partnership—can tackle complex agricultural challenges effectively.

References

Bagavathiannan, M. V., McCurdy, J. D., Brosnan, J. T., & McElroy, J. S. (2018). National team to use $5.7 million USDA award to address annual bluegrass epidemic in turfgrass. Texas A&M AgriLife News.

Grubbs, B., McCurdy, J., & Bagavathiannan, M. (2019). Poa annua: A plan of action. Golf Course Management Magazine.

Rutland, C. A., Brosnan, J. T., McElroy, J. S., & Zuk, J. W. (2023). Survey of target site resistance alleles conferring resistance in Poa annua. Crop Science, 63(5), 3110-3121.

McCurdy, J. D., and others (2023). Developing and implementing an integrated weed management program for herbicide resistant Poa annua. Crop, Forage & Turfgrass Management, 9(1), e20225.

Allen, J. H., and others (2022). Herbicide resistance in turf systems: insights and options for managing complexity. Sustainability, 14(21), 13399.

USDA-NIFA. (2020–2022). ResistPoa Project Extension and Training Outputs. USDA-NIFA Annual Reports.