How to Kill Shepherd's Purse in Perennial Ryegrass Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Shepherd's Purse in Perennial Ryegrass without damaging your turf, apply Tenacity (Mesotrione 40%), SpeedZone Lawn Weed Killer (2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62%) when air temperatures are between 55°F and 85°F.
Auxin herbicides translocate through the basal leaves and cause rapid stem epinasty within 24 hours.
1. Labeled Safe Herbicides That Kill Shepherd's Purse in Perennial Ryegrass
| 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 |
| SpeedZone Lawn Weed Killer EPA Reg. 2217-833 |
2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62% Group 4 + Group 14 (Synthetic Auxins + PPO Inhibitor) |
50°F – 85°F Rainfast: 3h |
Do NOT add surfactant. Adding NIS or MSO increases ester volatility and causes severe contact burn on desirable cool-season turf. | Check Price at DoMyOwn View on Amazon |
| Barricade 4FL (Prodiamine 65 WDG) EPA Reg. 100-1139 |
Prodiamine 40.7% (or 65% WDG) Group 3 (Microtubule Assembly Inhibitor / Dinitroaniline) |
45°F – 90°F Rainfast: 0h |
Pre-emergent soil barrier: do NOT use foliar surfactant. Must be watered in with 0.5 inches of irrigation or rainfall within 14 days of application to activate. | Check Price at DoMyOwn View on Amazon |
3. Optimal Seasonal Timing & Temperature Thresholds
Apply in late autumn during rosette stage or very early spring before seed pods expand.
Fall pre-emergent Prodiamine prevents germination entirely.
4. Diagnostic Checklist: Confirm It Is Shepherd's Purse Before Spraying
- Distinct flat, triangular to heart-shaped seed pouches resembling antique leather purses
- Basal rosette of deeply lobed leaves similar to young dandelion foliage
- Tall, slender flower stems topped by tiny four-petaled white cruciform flowers
Not 100% sure? Use our AI Photo Weed Scanner or review the full Shepherd's Purse Botanical Profile.