Use 0.094-0.25 lbs of clethodim per acre for most grassy weeds
Clethodim application rates vary by weed type and growth stage. For annual grasses, apply 0.094-0.125 lbs/acre; for tough perennials like bermudagrass or johnsongrass, use 0.18-0.25 lbs/acre. Always add a non-ionic surfactant (0.25-0.5% v/v) and apply to actively growing weeds for best results.
Key Factors Affecting Clethodim Rates
- Weed species: Annual grasses (e.g., crabgrass) require lower rates; perennials need higher doses.
- Growth stage: Young, actively growing weeds absorb herbicide better. Avoid treating stressed or dormant plants.
- Water volume: Use 10-20 gallons/acre for ground applications; 3-5 gallons/acre for aerial spraying.
- Adjuvants: A crop oil concentrate (1% v/v) or methylated seed oil improves efficacy in hard-to-control weeds.
Clethodim Rate Comparison by Weed Type
| Weed Type | Rate (lbs/acre) | Growth Stage | Surfactant Needed? | Reapplication Interval |
|---|---|---|---|---|
| Annual grasses (foxtail, crabgrass) | 0.094-0.125 | 2-6 leaf stage | Yes (0.25% v/v) | 14+ days if needed |
| Perennial grasses (quackgrass, bermudagrass) | 0.18-0.25 | 6-12 inches tall, pre-boot | Yes (0.5% v/v + COC) | 21+ days |
| Johnsongrass (rhizome suppression) | 0.25 | 18-24 inches tall | Yes (1% v/v COC) | 30+ days |
Application Best Practices
- Timing: Apply in morning/evening to reduce UV degradation. Avoid rain within 6 hours of spraying.
- Mixing: Pre-mix clethodim with water + surfactant in the spray tank before adding other herbicides.
- Sprayer calibration: Ensure uniform coverage with medium-sized droplets (200-400 microns).
- Tank cleanout: Rinse with ammonia solution (1 qt/100 gal water) to prevent cross-contamination.
Safety and Restrictions
- Pre-harvest interval (PHI): 30-60 days for most crops (check label for specifics).
- Rotational crops: Wait 30 days before planting non-labeled crops (e.g., legumes, vegetables).
- Toxicity: Low mammalian toxicity but highly toxic to aquatic invertebrates. Avoid drift near water bodies.
- PPE: Wear chemical-resistant gloves, long sleeves, and eye protection during handling.
Signs of Overapplication
- Crop injury: Yellowing or stunting in broadleaf crops (e.g., soybeans, cotton).
- Weed regrowth: Incomplete kill, especially in perennials, indicating resistance or insufficient rate.
- Residual soil activity: Clethodim has no soil residual; symptoms suggest misapplication or tank contamination.