Clethodim: A Post-Emergence Grass Herbicide for Broadleaf Crops
Technical Introduction
Clethodim (IUPAC: 2-[(E)-N-[(3-chloro-2-propyl-2-propenyl)oxy]oxime]-3-hexylcyclohex-2-en-1-one) is a selective, post-emergence herbicide belonging to the cyclohexanedione (DIM) chemical family.
It works by inhibiting acetyl-CoA carboxylase (ACCase), an essential enzyme in fatty acid biosynthesis, which is critical for cell membrane formation in plants. Inhibition leads to growth arrest and death of susceptible grass weeds.
Mode of Action: ACCase inhibitor (HRAC Group A).
Systemicity: Absorbed by leaves and translocated to meristematic tissue.
Selectivity: Safe for broadleaf crops, including soybeans, peanuts, and sunflowers.
Applications
Crops:
Soybeans, peanuts, sunflowers
Vegetables: beans, peas, carrots, potatoes
Oilseed rape (canola)
Weeds Controlled:
Annual grasses: Lolium spp. (ryegrass), Avena fatua (wild oats), Setaria spp. (foxtail grasses), Echinochloa crus-galli (barnyardgrass)
Perennial grasses: Cynodon dactylon (bermudagrass), Sorghum halepense (Johnson grass)
Advantages
Highly Selective: Targets grass weeds while sparing broadleaf crops.
Systemic Activity: Moves to growing points for complete weed control.
Post-Emergence Flexibility: Can be applied after weeds and crops have emerged.
Effective on Perennial Grasses: Controls rhizomatous and tillering grasses.
Low Environmental Impact: Breaks down relatively quickly in soil; low leaching potential.
Specifications (Typical Parameters)
| Parameter | Description | Typical Value |
|---|---|---|
| Chemical Name | Clethodim | |
| Chemical Class | Cyclohexanedione (DIM) herbicide | |
| Chemical Formula | C₁₆H₂₇NO₃ | |
| Molecular Weight | ~277.4 g/mol | |
| Appearance | Colorless to light amber liquid | |
| Purity (TC) | ≥ 95% | |
| Common Formulations | 240 g/L EC, 120 g/L EC | |
| Mode of Action | ACCase inhibitor (systemic) | |
| Target Weeds | Annual and perennial grasses | |
| Residual Activity | Short to moderate | |
| Toxicity | Oral LD₅₀ (rat) > 2,500 mg/kg (low toxicity); slightly toxic to aquatic organisms |
FAQ
Q1: What crops can Clethodim be used on?
A: It is mainly used in broadleaf crops such as soybeans, peanuts, sunflowers, and vegetables.
Q2: Which weeds does Clethodim control?
A: Effective against annual grasses (wild oats, ryegrass, foxtail) and some perennial grasses (bermudagrass, Johnson grass).
Q3: Is Clethodim systemic or contact?
A: Clethodim is systemic, absorbed by leaves and translocated to growing points for complete weed kill.
Q4: Can it be tank-mixed with other herbicides?
A: Yes, often mixed with broadleaf herbicides to control both grass and broadleaf weeds.
Q5: Is resistance an issue with Clethodim?
A: Yes. Resistance has been observed in ryegrass and wild oats. Crop rotation and herbicide rotation are recommended.
Q6: What is the typical application rate?
A: Usually 0.3–0.8 L/ha depending on crop, weed species, and growth stage.
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