S-Metolachlor Mode of Action: How It Works and Why It Matters
What Is S-Metolachlor?
S-metolachlor is a selective, systemic pre-emergent herbicide used to control annual grasses and certain broadleaf weeds in crops like corn, soybeans, cotton, and peanuts.
S-metolachlor is a refined version of metolachlor that contains a higher proportion of the biologically active S-isomer. This isomer enrichment increases herbicidal activity, allowing you to achieve the same or better weed control with lower application rates. For importers, distributors, and brand owners, this means more efficient use of active ingredients and greater flexibility in meeting residue and sustainability requirements.
S-Metolachlor Mode of Action
The mode of action of S-metolachlor is to inhibit the biosynthesis of very long-chain fatty acids (VLCFAs) in germinating weed seedlings, stopping cell division and elongation.
S-metolachlor belongs to the chloroacetanilide chemical family and is classified as a Group K3 herbicide under the HRAC classification. After soil application, it is absorbed primarily through shoots and roots of emerging weed seedlings. Once inside, it blocks the VLCFA pathway, which prevents new cell membranes from forming. This halts cell division and stops shoots and roots from growing beyond early stages.
| Aspect | S-Metolachlor |
|---|---|
| Chemical Group | Chloroacetanilide |
| HRAC Classification | Group K3 (Lipid Synthesis Inhibitor) |
| Site of Action | Shoots and roots of seedlings |
| Primary Action | Inhibits VLCFA biosynthesis |
| Result | Stops cell division and elongation |
Target Weed Spectrum
S-metolachlor works best against annual grasses and some small-seeded broadleaf weeds.
Your growers and downstream retailers should know that S-metolachlor has a broad spectrum but is primarily valued for controlling tough grass species. Common targets include:
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Barnyardgrass
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Foxtail species
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Crabgrass
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Johnsongrass (seedling)
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Wild oats
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Some broadleaf weeds like pigweed and lambsquarters (depending on the rate and crop)
It’s important to match the use rate and soil conditions to local weed pressure. In many weed management programs, S-metolachlor is tank-mixed or premixed with other herbicides to expand the spectrum and improve residual control.
Resistance Management & Best Practices
Rotating modes of action and using integrated weed management helps protect S-metolachlor’s effectiveness.
Like any herbicide, repeated reliance on a single mode of action increases the risk of resistance. To prevent this, importers and distributors should advise growers to:
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Use S-metolachlor in rotation with herbicides from other HRAC groups.
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Apply pre-emergent products at recommended rates for full residual effect.
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Combine with cultural practices like crop rotation, tillage, or cover crops.
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Monitor fields for early signs of weed escapes or shifts in dominant species.
Proper stewardship protects your portfolio’s reputation and your brand’s long-term sales potential.
Formulations & OEM Supply
A strong OEM partner ensures you get stable, compliant S-metolachlor formulations and packaging tailored to your market’s needs.
Whether you sell stand-alone S-metolachlor or custom tank mixes, you need consistent quality and proper documentation. Typical formulations include:
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EC (Emulsifiable Concentrate): Easy to mix and widely used for field spraying.
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GR (Granules): For direct soil application.
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Premix solutions: Often combined with atrazine, mesotrione, or glyphosate for broader-spectrum control.
Your OEM manufacturer should provide batch traceability, full COA, SDS, and stability data. You may also need custom labels in multiple languages, flexible packaging sizes (from 1 L bottles to bulk drums), and registration support for different export markets.
Working with a trusted supplier means fewer regulatory delays, lower storage risks, and smoother distribution — giving your distributors and local partners more confidence in your brand.
Need a quote?
Choosing the right pre-emergent herbicide starts with understanding how it works. If you want a reliable supply of high-quality S-metolachlor, we’re ready to help.
At POMAIS, we support importers, distributors, and brand owners with:
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Flexible OEM and private label services.
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Stable, compliant formulations for diverse markets.
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Clear regulatory documentation and expert technical support.
Contact us today to request product samples, check available pack sizes, or learn how to expand your herbicide line with a proven mode of action growers trust.
