S-Metolachlor Herbicide | Advanced Pre-Emergence Weed Control

S-Metolachlor is a selective, pre-emergence herbicide from the chloroacetanilide family, engineered to control annual grasses and broadleaf weeds in major crops like soybeans, corn, cotton, and vegetables. As the active stereoisomer of metolachlor, it delivers superior efficacy at lower application rates, reducing environmental impact while maintaining robust residual control. Ideal for pre-plant or pre-emergence applications, S-Metolachlor is trusted by growers worldwide for its reliability in diverse cropping systems.

Technical Specifications

Active Ingredient: S-Metolachlor (CAS No. 87392-12-9)
Formulation: 960g/L EC (Emulsifiable Concentrate)
Mode of Action: Inhibits very-long-chain fatty acid (VLCFA) synthesis in germinating weed seeds.
Target Crops: Soybeans, corn, cotton, peanuts, vegetables (e.g., tomatoes, peppers).
Target Weeds:
- Annual Grasses: Foxtail, crabgrass, barnyardgrass, annual bluegrass.
- Broadleaf Weeds: Pigweed, lambsquarters, ragweed, velvetleaf.
- Control Spectrum: Up to 30+ weed species.

Mode of Action

S-Metolachlor works by:

Absorbing into germinating weed seeds through soil moisture.
Inhibiting VLCFA synthesis, disrupting cell membrane formation.
Preventing root and shoot development, leading to seedling death before emergence.

Application Guide

Crop	Target Weeds	Formulation	Dosage (L/ha)	Application Timing
Soybeans	Annual grasses, pigweed	960g/L EC	1.0–1.5	Pre-plant incorporated or pre-emergence
Corn	Foxtail, lambsquarters	960g/L EC	1.2–2.0	Pre-plant or pre-emergence
Cotton	Crabgrass, morningglory	960g/L EC	0.8–1.2	Pre-plant or pre-emergence
Vegetables	Annual grasses, broadleaf	960g/L EC	0.5–1.0	Pre-plant or pre-emergence

Key Advantages

Enhanced Efficacy: Up to 2x more active than racemic metolachlor, requiring lower dosages.
Long Residual Control: 4–6 weeks of soil activity, reducing the need for multiple applications.
Crop Safety: Labeled for use in major row crops with minimal risk of phytotoxicity.
Resistance Management: Ideal partner for glyphosate or ALS inhibitors (e.g., Group 2 herbicides).
Flexible Application: Compatible with tillage systems (conventional, reduced, no-till).

Safety & Environmental Notes

Toxicity: Low acute toxicity to mammals; moderate toxicity to aquatic organisms.
Environmental Impact:
- Low volatility; minimal risk of off-target drift.
- Degrades via microbial activity (half-life: 15–30 days).
Storage: Store in cool, dry conditions; avoid freezing.

Resistance Management

HRAC Group: 15 (VLCFA inhibitors).
Strategies:
- Rotate with Group 2 (ALS inhibitors), Group 4 (synthetic auxins), or Group 14 (PPO inhibitors).
- Tank mix with residual herbicides (e.g., atrazine, saflufenacil).

FAQ

Can S-Metolachlor be used in no-till systems?
Yes, it is effective in no-till when applied with a burndown herbicide (e.g., glyphosate).
What is the rainfast period?
1–2 hours; absorbed quickly into soil colloids.
Is it safe for rotational crops?
Yes, with normal rotational intervals (check label for specific crops).
Can it control glyphosate-resistant weeds?
Yes, it targets a different mode of action, making it effective against resistant biotypes.

Packaging & OEM Services

Standard Packaging:
- 1L, 5L, 10L, 20L COEX containers.
- 200L drums for bulk orders.
Custom Solutions:
- Private labeling with multilingual artwork.
- Regulatory support for global markets.
- Custom formulations (e.g., S-Metolachlor + atrazine blends).

Why Choose S-Metolachlor?

Proven Performance: Trusted by growers for consistent pre-emergence weed control.
Sustainability: Reduced application rates minimize environmental footprint.
Technical Support: Expert guidance on application timing and tank mix compatibility.

Contact us for bulk orders, samples, or technical documentation. Elevate your weed management strategy with S-Metolachlor—precision herbicide technology for modern agriculture.

Mechanism of Action of S-Metolachlor

S-Metolachlor, a selective pre-emergence herbicide in the chloroacetanilide class, controls annual grasses and broadleaf weeds through a unique biochemical pathway. Below is a detailed breakdown of its mode of action from molecular targeting to field-level efficacy:

1. Selective Uptake and Translocation

Soil Adsorption: S-Metolachlor adsorbs to soil organic matter, forming a uniform herbicidal layer (0–5 cm depth) that intercepts germinating weed seeds.
Absorption Pathways:
- Root & Shoots: Primarily absorbed by coleoptiles (monocots) or hypocotyls (dicots) of germinating seedlings.
- Seed Uptake: Inhibits cell division directly within the seed during germination.
Translocation: Moves upward via xylem to meristematic tissues (root tips, shoot apices) where growth is actively occurring.

2. Molecular Target: Inhibition of VLCFA Synthesis

Target Enzyme: Blocks fatty acid elongase (FAE), a key enzyme in the biosynthesis of very-long-chain fatty acids (VLCFA).
Action Mechanism:
1. FAE catalyzes the elongation of C16/C18 fatty acids to C20–C34 VLCFA, essential for cell membrane and cuticle formation.
2. S-Metolachlor disrupts FAE activity, preventing VLCFA production.
Downstream Effects:
- Cell Membrane Damage: Disrupted VLCFA synthesis weakens cell membranes, causing leakage and cell death.
- Cuticle Deficiency: Reduced cuticle formation leads to water loss and wilting.
- Meristem Arrest: Cell division in root and shoot tips is halted, resulting in stunted growth.

3. Differential Impact on Weed Species

Weed Type	Sensitive Tissues	–
Grasses (Monocots)	Coleoptile, plumule	Swollen, twisted shoot tips unable to penetrate soil (“goose neck” deformity).
Broadleaves (Dicots)	Hypocotyl, cotyledons	Curled cotyledons, sparse root hairs, necrotic growing points.
Sedges (Cyperaceae)	Underground tubers	Blocked new shoot emergence, rotting old roots, overall yellowing.

4. Crop Selectivity Mechanisms

Metabolic Detoxification:
- Crops (e.g., corn, soybeans): Express cytochrome P450 enzymes (e.g., CYP71A1) that hydroxylate S-Metolachlor into non-toxic metabolites.
- Weeds: Lack efficient detoxification pathways, leading to VLCFA depletion and cell death.
Uptake & Translocation: Crops may exhibit reduced absorption or slower translocation to meristematic tissues.

5. Environmental Factors Affecting Efficacy

Soil Moisture: Optimal activity requires 10–15 mm of rainfall or irrigation to activate soil adsorption and seedling uptake.
Soil Organic Matter: Higher OM (＞2%) may require higher doses to maintain effective herbicidal layers.
Temperature: Optimal performance at 15–25°C; reduced activity in cold or hot conditions.

6. Resistance Management Considerations

HRAC Group 15: As a VLCFA inhibitor, S-Metolachlor is part of a unique mode of action, making it valuable for rotating with other herbicide groups (e.g., Group 2, 4, 14) to delay resistance development.
Synergistic Tank Mixes: Often combined with atrazine or glyphosate to broaden weed spectrum and enhance residual control.

7. Field Efficacy Timeline

0–3 days post-application: S-Metolachlor forms a soil herbicide barrier.
3–7 days: Germinating weeds absorb the herbicide, leading to VLCFA depletion.
7–14 days: Visible symptoms (stunted growth, chlorosis, necrosis) appear in susceptible weeds.
14–28 days: Complete weed death; residual control lasts 4–6 weeks depending on soil conditions.

Summary

S-Metolachlor’s mechanism combines selective uptake, VLCFA biosynthesis inhibition, and crop-specific detoxification to provide robust pre-emergence weed control. Its efficacy relies on precise timing with weed germination, making it a cornerstone in integrated weed management (IWM) programs for major row crops.