Clomazone 96%: A Selective Pre-Emergent Herbicide

Definition:
Clomazone is a selective, pre-emergent and early post-emergent herbicide widely used to control annual grasses and broadleaf weeds. It is primarily applied in crops such as soybeans, cotton, peanuts, tobacco, and certain vegetables. Its high effectiveness and unique mode of action make it an important component in integrated weed management programs.

Chemical Characteristics of Clomazone:

• Chemical Name: 2-(2-chlorobenzyl)-4,4-dimethyl-1,2-oxazolidin-3-one

• Molecular Formula: C₁₂H₁₄ClNO₂

• Molecular Weight: 239.7 g/mol

• Appearance: Clear to pale yellow liquid (technical grade 96%).

• Solubility: Slightly soluble in water; readily soluble in organic solvents.

• Stability: Stable under normal storage conditions; sensitive to strong light exposure which may cause degradation.

Mode of Action:

Clomazone inhibits the DOXP (1-deoxy-D-xylulose 5-phosphate) synthase enzyme, which disrupts carotenoid biosynthesis in plants. This leads to chlorophyll degradation, causing bleaching symptoms in susceptible weeds and eventual death.

Uses and Applications:

1. Weed Control Spectrum:

   • Effective against annual grasses (e.g., barnyard grass, foxtail).

   • Controls small-seeded broadleaf weeds (e.g., pigweed, lambsquarters, morning glory).

2. Crop Usage:

   • Commonly used in soybeans, cotton, peanuts, tobacco, sugarcane, and vegetables (such as pumpkins and squash).

3. Application Timing:

   • Pre-emergence: Applied before weed germination for residual control.

   • Early Post-emergence: Effective on very young weed seedlings.

Benefits of Clomazone:

• Selective Action: Safe on labeled crops when applied correctly.

• Broad-Spectrum Control: Targets both grass and broadleaf weeds.

• Residual Activity: Provides extended weed suppression in early crop growth stages.

• Resistance Management: Unique mode of action helps reduce resistance development.

Limitations:

• Bleaching Drift Risk: Volatility can cause off-target bleaching in nearby sensitive crops.

• Soil Dependence: Effectiveness is influenced by soil type and organic matter content.

• Limited Post-Emergence Control: Works best pre-emergence or on very early weed stages.

Recommended Application:

• Dosage: 0.5–1.0 kg active ingredient per hectare (varies by crop and weed pressure).

• Method: Uniform soil surface spray followed by incorporation or rainfall for activation.

• Precautions:

  • Avoid drift to non-target crops.

  • Apply under calm wind conditions to minimize volatilization.

  • Use protective clothing and follow label instructions strictly.

Storage and Handling:

• Storage: Store in sealed, original containers in a cool, dry, and well-ventilated area.

• Shelf Life: Typically 2–3 years under proper storage conditions.

• Safety: Keep away from food, feed, and water sources.

FAQ on Clomazone:

Q1: What weeds does Clomazone control best?
A1: It is particularly effective against annual grasses and small-seeded broadleaf weeds.

Q2: Is Clomazone systemic?
A2: Yes, it is absorbed by roots and shoots, then translocated within the plant.

Q3: Can Clomazone cause crop bleaching?
A3: Yes, temporary bleaching can occur but is usually reversible and does not harm crop yield.

Q4: Can Clomazone be mixed with other herbicides?
A4: Yes, it is often tank-mixed with other herbicides to broaden weed control spectrum.