Controlling annual bluegrass in warm-season lawns
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August 12, 2026
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By Lane Tredway, Ph.D., technical services manager for SyngentaAnnual bluegrass (
Poa annua) is a challenging weed to manage in any setting, but control is particularly difficult in warm-season grasses. This is because annual bluegrass grows as a winter annual, germinating in late summer to fall and gradually maturing through the winter and early spring. During this time, the warm-season grass offers little competition against weed infestations which can become unsightly in the spring to early summer.
Herbicide programs incorporating pre- and post-emergent products can offer excellent control of annual bluegrass, but proper product selection and application timing are crucial. Herbicides vary in their turf safety across warm-season species, so the first step is to determine the options at your disposal. Then, the applications should be timed appropriately to maximize their performance.
| Product | Mode of Action | Turf Species Labeled for Application |
| Bermudagrass | Centipedegrass | St. Augustinegrass | Zoysiagrass |
| BarricadeĀ® 4FL herbicide or Barricade 65WG herbicide | pre-emergent | ā | ā | ā | ā |
| MonumentĀ® 75WG herbicide | post-emergent | ā |
|
| ā |
| RecognitionĀ® herbicide | post-emergent | ā |
| ā | ā |
| PrincepĀ® Liquid herbicide | pre- and post-emergent | ā | ā | ā | ā |
| RewardĀ® herbicide | post-emergent | ā dormant applications only |
|
| ā dormant applications only |
- Barricade 4FL and Barricade 65WG: Pre-emergent herbicides labeled for application to the warm-season turf species listed above.
- For best results, the first application of Barricade should be made before soil temperatures decline below 70Ā°F.
- Monument 75WG and Recognition: Post-emergent herbicides that both contain the active ingredient trifloxysulfuron.
- Recognition also contains a proprietary safener that enables its use on St. Augustinegrass with excellent turf safety.
- These products excel as early-post emergent treatments applied in October or November, after the majority of annual bluegrass germination has occurred.
- Reward: A contact, non-selective herbicide that may be applied to bermudagrass or zoysiagrass when they are completely dormant without negatively impacting spring green-up.
- Applications in January or February can provide excellent annual bluegrass control and clean up any other labeled winter annual weeds that may have escaped earlier treatments.
- Princep Liquid: Serves primarily as a pre-emergent herbicide but also enhances the post-activity of other herbicides like Monument 75WG, Recognition and Reward.
Below is an example of how to best incorporate these products into an annual bluegrass program for bermudagrass and zoysiagrass turf.
| App. # | Approx. Date | Product Description | Rate/acre | Comments |
| 1 | Oct. 1 | BarricadeĀ® 4FL herbicide | 16 fl. oz. | Apply when 5-day average soil temperatures decline to 70Ā°F. |
| 2 | Nov. 1 | Barricade 4FL +
PrincepĀ® Liquid herbicide +
MonumentĀ® 75WG herbicide +
āāāāāāānon-ionic surfactant | 16 fl. oz.
32 fl. oz.
0.35 oz.
0.25% v/v | Apply 4 to 6 weeks after initial application. |
| 3 | Jan. or Feb. | Barricade 4FL +
RewardĀ® herbicide +
Princep Liquid +
non-ionic surfactant | 16 fl. oz.
32 fl. oz.
32 fl. oz.
0.25% v/v | Dormant application. |
Visit
GreenCastOnline.com/LawnPrograms to see recommended programs for other turf species.
Ā© 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. BarricadeĀ®, GreenCastĀ®, MonumentĀ®, PrincepĀ®, RecognitionĀ®, RewardĀ® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective third-party owners.