Metolachlor
Metolachlor: Premium Herbicide for Effective Weed Control
Metolachlor is a powerful selective herbicide widely used for pre-emergence and early post-emergence control of annual grasses and certain broadleaf weeds in various crops. With over three decades of proven performance, Metolachlor remains a cornerstone in modern agricultural weed management programs.
Key Product Specifications
- Chemical Name: 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide
- Molecular Formula: C15H22ClNO2
- CAS Number: 51218-45-2
- Appearance: Clear to light amber liquid
- Odor: Mild aromatic
- Solubility: 530 mg/L in water at 20°C
- Vapor Pressure: 1.7 × 10⁻⁵ mmHg at 20°C
- Storage: Store in original container below 30°C
Technical Parameters
| Parameter | Value |
|---|---|
| Active Ingredient Content | 960 g/L |
| Formulation Type | Emulsifiable Concentrate (EC) |
| Specific Gravity | 1.12 g/cm³ at 20°C |
| pH (1% solution) | 6.0-8.0 |
| Flash Point | ≥100°C |
| Shelf Life | 2 years in sealed original container |
Application Guidelines
| Crop | Application Rate | Application Timing | Weeds Controlled |
|---|---|---|---|
| Corn | 1.5-2.0 L/ha | Pre-plant or pre-emergence | Foxtails, crabgrass, barnyardgrass |
| Soybeans | 1.0-1.7 L/ha | Pre-emergence | Annual grasses, pigweed, lambsquarters |
| Cotton | 1.2-2.0 L/ha | Pre-plant incorporated | Goosegrass, morningglory |
| Peanuts | 1.0-1.5 L/ha | Pre-emergence | Texas panicum, broadleaf signalgrass |
Metolachlor Frequently Asked Questions
Q: What is the mode of action of Metolachlor?
A: Metolachlor works primarily by inhibiting cell division in susceptible weeds, specifically targeting the shoot meristems. It interferes with very long chain fatty acid (VLCFA) synthesis, which is essential for cell membranes and cuticular wax production in developing seedlings. This mode of action makes it particularly effective against germinating annual grasses and small-seeded broadleaf weeds when applied at the proper timing.
Q: How long does Metolachlor remain active in the soil?
A: The soil persistence of Metolachlor depends on several factors including soil type, organic matter content, temperature, and moisture. Typically, it provides residual control for 6-10 weeks. In coarse-textured soils with low organic matter, degradation occurs more rapidly (4-6 weeks), while in fine-textured soils with higher organic matter, activity may persist up to 12 weeks. Microbial degradation is the primary breakdown pathway, with half-life ranging from 15 to 70 days under typical field conditions.
Q: Can Metolachlor be tank-mixed with other herbicides?
A: Yes, Metolachlor is frequently tank-mixed with other herbicides to broaden the weed control spectrum. Common tank mix partners include atrazine for corn, metribuzin for soybeans, and pendimethalin for cotton. Always follow label recommendations for compatibility and observe all restrictions regarding crop stage, soil type, and application rates. A jar test is recommended when mixing with unfamiliar products or when adding adjuvants.
Environmental and Safety Information
- Toxicity Class: III (Slightly hazardous)
- Oral LD50 (rat): > 2,000 mg/kg
- Dermal LD50 (rabbit): > 2,000 mg/kg
- Ecotoxicity: Highly toxic to aquatic organisms
- PPE Requirements: Long-sleeved shirt, long pants, chemical-resistant gloves, shoes plus socks
- REI: 12 hours for most crops
Metolachlor Benefits
Metolachlor offers several advantages in modern weed management programs:
- Provides excellent residual control of grass weeds
- Flexible application timing (pre-plant through early post-emergence)
- Multiple formulation options for different use scenarios
- Proven performance across diverse geographies
- Cost-effective solution compared to many alternatives
- Well-established resistance management profile
Storage and Handling
Proper storage of Metolachlor is essential for maintaining product efficacy and ensuring safety:
- Store in original containers with intact labels
- Keep containers tightly closed when not in use
- Maintain storage temperature between 5°C and 30°C
- Protect from freezing and direct sunlight
- Store away from food, feed, and drinking water
- Keep out of reach of children and animals
Metolachlor Frequently Asked Questions (Continued)
Q: What are the symptoms of Metolachlor injury in susceptible weeds?
A: Affected weeds typically exhibit stunted growth, malformed or crinkled leaves, and failure of the shoot to emerge properly from the coleoptile in grasses. Broadleaf weeds may show thickened hypocotyls, swollen root tips, and reduced root hair development. Symptoms often appear within 7-14 days after application under favorable growing conditions. The herbicide is most effective when applied to moist soil and followed by irrigation or rainfall (0.5-1 inch) to activate the chemical in the weed germination zone.
Q: Are there any rotational crop restrictions after using Metolachlor?
A: Yes, rotational intervals vary by crop and soil conditions. Generally, wait 4 months before planting small grains; 9 months for sugarbeets, potatoes, and other root crops; and 12 months for vegetables in coarse-textured soils. Always consult the specific product label for detailed restrictions based on your soil type and application rate. Conduct a bioassay if uncertain about potential carryover effects to sensitive rotational crops.
Q: How does soil moisture affect Metolachlor performance?
A: Soil moisture is critical for optimal Metolachlor performance. The herbicide needs approximately 0.5-1 inch of rainfall or irrigation within 7-10 days after application to properly incorporate into the weed germination zone. In dry conditions, efficacy decreases significantly as the chemical remains bound to soil particles near the surface. However, excessive rainfall (more than 2 inches shortly after application) may lead to leaching in sandy soils, potentially causing crop injury or reduced weed control in parts of the field.
Compatibility Information
Metolachlor demonstrates excellent compatibility with many common agricultural inputs:
| Compatible With | Notes |
|---|---|
| Most liquid fertilizers | Perform jar test with specific formulation |
| Common fungicides | Check for pH sensitivity |
| Many insecticides | Avoid organophosphate combinations in some cases |
| Other herbicides | Most common pre-mix partners |
Metolachlor Resistance Management
While resistance to Metolachlor is relatively rare, proper stewardship is essential:
- Rotate with herbicides having different modes of action
- Use full labeled rates for target weeds
- Combine with residual partners when possible
- Monitor fields for reduced performance
- Implement cultural weed control practices
Metolachlor Frequently Asked Questions (Final Section)
Q: What is the difference between S-Metolachlor and racemic Metolachlor?
A: S-Metolachlor contains only the active S-isomer, while racemic Metolachlor contains both R and S isomers in equal proportions. The S-isomer is significantly more herbicidally active, allowing S-Metolachlor products to achieve comparable weed control at about 60-65% of the application rate of racemic Metolachlor. This results in reduced environmental loading while maintaining efficacy. Both forms share the same mode of action and weed control spectrum when applied at appropriate rates.
Q: How should Metolachlor be disposed of if unused?
A: Never dispose of unused Metolachlor by pouring it onto the ground, into waterways, or into drains. Follow all local regulations for pesticide disposal. Options typically include: 1) Using the product according to label directions on an approved site, 2) Participating in agricultural chemical collection programs, 3) Consulting with waste disposal specialists licensed for pesticide handling. Triple rinse empty containers and dispose of them according to local regulations.
Q: What should I do if Metolachlor spills occur?
A: For small spills (<1 gallon), contain the liquid with absorbent materials like vermiculite, clay, or pet litter. Wear appropriate PPE during cleanup. For larger spills, immediately contact local environmental authorities. Prevent spill runoff from entering drains, waterways, or groundwater. Contaminated soil should be excavated and disposed of properly. Never wash spills into storm sewers or allow to enter surface waters. Keep spill control materials on hand when handling large quantities.