By Lane Tredway, Ph.D., technical services manager for Syngenta

Pennant Magnum^® Herbicide | Timing and Rates | Broad-Spectrum Control 

Goosegrass (Eleusine indica) is one of the most difficult weeds to manage in turf. It produces abundant seedheads below the mowing height, thrives in compacted soils and tolerates moisture and heat stress. Additionally, populations that are resistant to several classes of herbicides have been reported. Fortunately, Pennant Magnum^® herbicide offers an effective pre-emergent solution for managing goosegrass before it becomes a problem.

Goosegrass is a summer annual grass that begins germinating when soil temperatures reach approximately 63° F in spring. It thrives in compacted soils and areas where turf is weakened by heavy traffic or environmental stress. In southern climates, goosegrass can even persist as a perennial, making control particularly challenging.

Why choose Pennant Magnum?

Pennant Magnum, containing the active ingredient s-metolachlor, provides several advantages compared to other pre-emergent herbicides:

1. Versatile application: Pennant Magnum is safe for application on a wide range of warm-season turfgrasses, including bermudagrass, centipedegrass, St. Augustinegrass, bahiagrass and zoysiagrass. Pennant Magnum is labeled for application to all turfgrass sites except golf course greens, tees and collars/aprons.
   1. For more information, download the Goosegrass Control in Warm-Season Turfgrasses sheet
2. Root-safe formulation: While many pre-emergent herbicides work by inhibiting root growth, Pennant Magnum is shoot-absorbed and doesn't negatively impact turfgrass root development.
3. Unique control spectrum: Beyond goosegrass, Pennant Magnum also controls doveweed, annual sedge, yellow nutsedge, crabgrass species and more than 20 additional turf and landscape weeds.

Optimal timing and rates for goosegrass control

• Apply Pennant Magnum in spring before soil temperatures reach 63° F. Sign up for Soil Temperature Alerts or download the GreenCast^® Connect app to receive alerts for goosegrass and other common turf pests.
• Make two applications at 21 fl. oz./A with a 6-week interval between treatments
  • Pennant Magnum is now available in 2.5-gallon containers to cover one application on 15 acres
• Apply in at least 10 gallons of water/A
• Water-in within 7 days if no rainfall occurs

Maximize weed control beyond goosegrass

For a broader spectrum of control and season-long results, Pennant Magnum can be mixed with other products such as Barricade^® herbicides (0.5-0.75 lbs. AI/A), Monument^® herbicide (10-15 grams of product/A) or Recognition^® herbicide (1.29-1.95 oz./A) depending on the turf species being managed. For examples of how to incorporate Pennant Magnum into a season long program, see our golf and lawn agronomic programs.

Pre-emergent goosegrass control in bermudagrass turf

Pennant Magnum + Barricade for goosegrass pre-emergent control

All photos are either the property of Syngenta or are used with permission.

© 2025 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. Barricade^®, GreenCast^®, Monument^®, Pennant Magnum^®, Recognition^® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are the property of their respective third-party owners.