How to Kill Nimblewill in Tall Fescue Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Nimblewill in Tall Fescue without damaging your turf, apply Tenacity (Mesotrione 40%), Pylex Herbicide (Topramezone 29.7%) when air temperatures are between 55°F and 85°F.
Nimblewill is extremely sensitive to HPPD inhibition. Mesotrione causes rapid bleaching (chlorosis) followed by plant collapse. Always add Non-Ionic Surfactant (NIS).
1. Labeled Safe Herbicides That Kill Nimblewill in Tall Fescue
| Recommended Product | Active Ingredient & Group | Application Temp (°F) | Surfactant & Mixing Protocol | Where to Buy |
|---|---|---|---|---|
| Tenacity EPA Reg. 100-1267 |
Mesotrione 40% Group 27 (HPPD Inhibitor) |
55°F – 85°F Rainfast: 6h |
Always apply with Non-Ionic Surfactant (NIS) at 1 tsp (5 mL) per gallon of water for post-emergent applications. Causes temporary white bleaching on susceptible weeds and turf tips. | Check Price at DoMyOwn View on Amazon |
| Pylex Herbicide EPA Reg. 7969-327 |
Topramezone 29.7% Group 27 (HPPD Inhibitor / Pyrazolone) |
55°F – 85°F Rainfast: 1h |
Must be applied with Methylated Seed Oil (MSO) at 1 to 1.5 tsp per gallon of water. Tank-mixing with Triclopyr Ester reduces white bleaching and speeds up Bermudagrass and Goosegrass mortality. | Check Price at DoMyOwn View on Amazon |
3. Optimal Seasonal Timing & Temperature Thresholds
Apply in late spring to early summer when Nimblewill is green and actively growing, and repeat applications in late summer if regrowth occurs.
Do not treat when Nimblewill is entering winter dormancy or drought-stressed, as lack of chlorophyll synthesis prevents Mesotrione uptake.
4. Diagnostic Checklist: Confirm It Is Nimblewill Before Spraying
- Fine-textured, short, grayish-green, flat leaf blades (1 to 2 inches long)
- Wiry, decumbent stems that root at lower nodes forming dense mats
- Turns straw-brown and completely dormant in late fall and winter
Not 100% sure? Use our AI Photo Weed Scanner or review the full Nimblewill Botanical Profile.