Research reveals game-changer against Poa annua invasion
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August 10, 2026
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By Lane Tredway, Ph.D., technical services manager for Syngenta
Recent research by Jim Brosnan, Ph.D. and his team at the University of Tennessee has uncovered an exciting new strategy to manage annual bluegrass (Poa annua) in bermudagrass tees, fairways and roughs – Trimmit® 2SC plant growth regulator.
Trimmit 2SC has long been used in the spring and early summer to suppress annual bluegrass in creeping bentgrass putting greens. However, applications to bermudagrass at this time can dramatically slow bermudagrass green-up. For this reason, it is generally not recommended to apply Trimmit 2SC to bermudagrass after March 15.
Dr. Brosnan on Trimmit 2SC recommendations: Excerpt from TurfNet webinar, "Poa Control Master Class."
Instead of spring applications, Dr. Brosnan’s group has shown that late summer to fall applications of Trimmit 2SC significantly suppress annual bluegrass without negatively affecting bermudagrass green-up the following spring. Applications from mid-August through December have provided the greatest benefit, reducing Poa invasion by as much as 85% through April of the following year.
Suppression of annual bluegrass with Trimmit 2SC in bermudagrass
Source: Jim Brosnan, Ph.D., University of Tennessee, 2024. Trial conducted on non-overseeded Tifway bermudagrass mowed at 0.5 in. Treatments applied three times on a 21-day interval (Aug. 27, Sept. 16 and Oct. 7, 2024). Photos taken on Feb. 3, 2025.For best results when using Trimmit for Poa suppression we recommend the following best practices:
- Apply Trimmit at 16 fl. oz./A on a 3- to 4-week interval
- Initiate applications in late summer when soil temperatures decline to 70°F, which is when annual bluegrass begins to germinate
- Applications from August through December have provided the greatest benefit in our trials without negatively impacting spring green-up
- Apply Trimmit with sufficient water volume (at least 40 gal./A) to ensure uniform coverage.
- Irrigate within 24 hours to help the active ingredient penetrate the thatch and so
With widespread herbicide resistance in annual bluegrass populations, many golf course superintendents are struggling to adequately control this weed. Trimmit 2SC offers a valuable new option to which there is no known resistance.
Prepare now and pay later with extended SummerPay™ program terms! Beginning Aug. 1, 2026, defer payment until June 11, 2027 on qualifying Trimmit 2SC purchases. Learn more
here.
For additional application and rate recommendations, download the
Poa Annua Suppression in Bermudagrass Turf with Trimmit 2SC information sheet.
Do not apply Trimmit 2SC to bermudagrass putting greens unless they are overseeded. Avoid use on residential lawns or athletic fields under heavy traffic. Refer to
the Trimmit 2SC label for all other precautions and restrictions.
For more information visit
GreenCastOnline.com/Trimmit2SC or
contact your local Syngenta territory manager.
All photos and videos are either the property of Syngenta or are used with permission.Performance assessments are based upon results or analysis of public information, field observations and/or internal Syngenta evaluations. Trial reflects treatment rates commonly recommended in the marketplace.
© 2026 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. GreenCast®, SummerPay™, Trimmit®, the Alliance Frame, the Purpose Icon and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective third-party owners.