Prometryn 250g/L + S-Metolachlor 250g/L: Pre-Emergence Herbicide for Annual Grass and Broadleaf Control

Introduction

Prometryn 250g/L + S-Metolachlor 250g/L is a selective combination herbicide designed mainly for pre-plant incorporated and pre-emergence control of susceptible annual grasses and broadleaf plants.

The formulation contains:

• Prometryn — 250g/L

• S-Metolachlor — 250g/L

Total active ingredient concentration:

500g/L

The two active ingredients complement each other:

Prometryn → strong activity against many annual broadleaf species and some annual grasses

S-Metolachlor → strong residual activity against annual grasses and some small-seeded broadleaf species

The combination is particularly useful in soil-applied programs where long residual activity and broad early-season control are required.

EPA labeling for S-Metolachlor specifically includes tank mixtures with Prometryn in cotton for preplant incorporated or preemergence application, confirming the technical compatibility and practical use logic of this combination.

What Is Prometryn + S-Metolachlor?

This product combines two selective herbicides with different modes of action.

Prometryn

Prometryn is a triazine herbicide used mainly for soil and early post-emergence applications in registered crops.

It is active against many:

• Annual broadleaf species

• Annual grasses

• Small-seeded annual plants

Prometryn interferes with photosynthesis in susceptible plants.

Its strongest practical role in this mixture is to broaden control of annual broadleaf species and complement the grass-control spectrum of S-Metolachlor.

EPA registration records for Prometryn list uses in cotton and multiple vegetable crops, with targets including annual broadleaf species and annual grasses.

How Does Prometryn Work?

Prometryn belongs to the photosystem II inhibitor group.

After uptake by roots or shoots, it interferes with electron transport in photosynthesis.

The process can be summarized as:

1. Prometryn is absorbed by susceptible plants.

2. Photosystem II electron transport is inhibited.

3. Normal energy production is disrupted.

4. Reactive damage develops in plant tissue.

5. Growth stops.

6. Susceptible plants die.

Because Prometryn is active against a broad group of annual species, it helps improve the overall spectrum of the combination.

What Is S-Metolachlor?

S-Metolachlor is a selective residual herbicide widely used in agricultural cropping systems.

Its main strength is control of:

• Annual grasses

• Some small-seeded broadleaf species

• Certain sedge species depending on label and conditions

It is most effective when present in the soil during germination and early seedling development.

EPA labels describe S-Metolachlor as a residual herbicide that is commonly used preplant incorporated or preemergence in crops such as cotton.

How Does S-Metolachlor Work?

S-Metolachlor inhibits the development of very-long-chain fatty acids in susceptible plants.

These fatty acids are essential for:

• Cell membrane formation

• Seedling growth

• Normal shoot development

• Early root development

When germinating seedlings absorb S-Metolachlor:

1. Normal lipid synthesis is disrupted.

2. Cell division and elongation are affected.

3. Shoots and roots develop abnormally.

4. Seedlings fail to establish.

5. Susceptible plants die before or shortly after emergence.

This is why S-Metolachlor is mainly used as a:

Pre-Emergence Residual Herbicide

Why Combine Prometryn and S-Metolachlor?

The two active ingredients provide complementary control.

Prometryn Contributes

• Strong annual broadleaf suppression

• Activity against some annual grasses

• Photosystem II inhibition

• Residual soil activity

S-Metolachlor Contributes

• Strong annual grass control

• Residual soil protection

• Early seedling suppression

• Activity against some small-seeded broadleaf species

Together, they provide a broader spectrum than either ingredient used alone.

The practical concept is:

Annual Grass Control + Broadleaf Control + Residual Soil Protection

Which Plants Can the Combination Control?

EPA S-Metolachlor labeling lists additional species controlled when S-Metolachlor is combined with Prometryn, including:

• Junglerice

• Wild oats

• Annual morningglory

• Groundcherry

• Hairy nightshade

• Lambsquarters

• Mustard

• Prickly sida

• Purslane

• Ragweed

• Shallow-germinating cocklebur seedlings

• Coffeeweed seedlings

The exact spectrum depends on:

• Crop

• Soil texture

• Application rate

• Timing

• Moisture

• Local registration

Which Crops Can Use This Combination?

The Prometryn + S-Metolachlor combination has a particularly strong technical basis in:

Cotton

EPA labeling specifically allows S-Metolachlor + Prometryn tank mixtures for cotton in registered programs.

Depending on national registration, similar active ingredients may also be used in other crop systems.

However, commercial claims should always follow the exact destination-market label.

Do not assume that a crop approved for Prometryn alone or S-Metolachlor alone is automatically approved for the combination.

Why Is Pre-Emergence Timing Important?

This mixture performs best when active ingredients are already present in the upper soil layer during seed germination.

Recommended application windows may include:

• Preplant incorporated

• At planting

• Preemergence

EPA labeling specifically describes Prometryn + S-Metolachlor applications in cotton as:

Preplant incorporated or preemergence.

The objective is to stop susceptible plants before they establish a competitive stand.

Why Is Soil Moisture Important?

Residual herbicides need sufficient soil moisture to become biologically active in the germination zone.

Without adequate moisture:

• Activation may be delayed

• Control can become uneven

• Seedlings may emerge before strong herbicide activity develops

EPA S-Metolachlor labeling states that in non-irrigated areas, if approximately 0.5 inch of rainfall does not occur within 10 days after application, shallow cultivation may be recommended under the label to improve incorporation.

This illustrates how closely residual performance depends on soil moisture and placement.

Why Is Soil Texture Important?

Soil texture strongly affects residual herbicide behavior.

Important factors include:

• Sand content

• Clay content

• Organic matter

• Moisture-holding capacity

Heavier soils and soils with higher organic matter may bind more herbicide.

Very light sandy soils may increase crop-injury risk under some conditions.

EPA labels for S-Metolachlor + Prometryn combinations contain soil-specific rate and use restrictions, demonstrating the importance of soil type in application decisions.

Why Is Incorporation Depth Important?

When applied preplant incorporated, the mixture should remain in the upper germination zone.

If incorporation is too deep:

• Herbicide concentration near germinating seeds may be reduced

• Control may become less consistent

If herbicide becomes concentrated in the crop seed furrow:

• Crop injury risk may increase

EPA labeling for S-Metolachlor + Prometryn in cotton includes specific precautions regarding planting depth and herbicide concentration in furrows.

Residual Activity

One of the main advantages of the combination is residual soil activity.

After correct application, the treated soil zone can suppress several flushes of germinating annual plants.

Residual duration depends on:

• Rate

• Soil texture

• Organic matter

• Rainfall

• Irrigation

• Temperature

• Microbial activity

This residual protection can reduce early crop competition and lower the need for immediate follow-up treatments.

Why Is Early-Season Control Important?

Early competition can significantly affect crop establishment.

During the first stages of crop growth, unwanted plants compete for:

• Water

• Nutrients

• Light

• Root space

A strong pre-emergence program helps establish a cleaner field during this critical period.

This allows the crop to develop a stronger canopy and root system before later-season competition begins.

Resistance Management

Prometryn and S-Metolachlor belong to different herbicide mode-of-action groups.

This gives the combination an advantage compared with relying on one active ingredient alone.

However, resistance management is still important.

A professional strategy should include:

• Rotation with different herbicide modes of action

• Crop rotation

• Mechanical control

• Field scouting

• Prevention of seed production by surviving plants

• Use of registered mixtures where appropriate

The presence of two active ingredients does not eliminate resistance risk.

Why Should Surviving Plants Be Monitored?

Repeated survival of the same species after correct herbicide application may indicate:

• Incorrect application

• Environmental failure

• Poor soil activation

• Herbicide resistance

Surviving plants should not be allowed to produce large quantities of seed.

Field monitoring is one of the simplest and most important resistance-management practices.

What Does 500g/L Mean?

The formulation contains:

Prometryn 250g/L + S-Metolachlor 250g/L

for a combined total of:

500g/L active ingredients

If the commercial formulation is EC, it may be described as:

500EC

provided that this matches the registered product specification.

The exact formulation type should always be confirmed before creating labels or marketing material.

Why Is Formulation Quality Important?

A high-quality liquid formulation should provide:

• Correct active ingredient concentration

• Uniform mixing

• Stable emulsion or dispersion

• Good storage stability

• Consistent batch quality

• Suitable packaging compatibility

Poor formulation may result in:

• Separation

• Crystallization

• Uneven application

• Reduced field consistency

For professional buyers, declared concentration alone is not enough.

OEM and Private Label Manufacturing

Prometryn 250g/L + S-Metolachlor 250g/L can be produced for OEM and private-label markets where registration permits.

Customization may include:

• Brand name

• Customer logo

• Bottle design

• Label language

• Package size

• Outer carton

• Market-specific artwork

Typical packaging may include:

• 250mL

• 500mL

• 1L

• 5L

• Other customized sizes

Final packaging must comply with destination-market pesticide regulations.

What Should Buyers Check Before Purchasing?

Professional buyers should verify:

Active Ingredient Content

Prometryn 250g/L

S-Metolachlor 250g/L

Total Concentration

500g/L

Formulation Type

Confirm whether the product is:

EC or another registered formulation

Technical Documents

Request:

• Certificate of Analysis — COA

• Safety Data Sheet — SDS

• Technical Data Sheet — TDS

• Product specification

Physical Quality

Evaluate:

• Appearance

• Stability

• Dilution behavior

• Active ingredient content

Batch Consistency

Different production batches should remain within agreed specification limits.

Frequently Asked Questions

How does Prometryn + S-Metolachlor control annual plants?

Prometryn inhibits photosynthesis, while S-Metolachlor disrupts very-long-chain fatty acid synthesis and early seedling development. Together they provide broad residual pre-emergence control.

How should this combination be applied?

It is mainly used in preplant incorporated or preemergence programs according to the registered crop label.

How does soil moisture affect performance?

Adequate moisture activates the herbicides in the germination zone and helps achieve more uniform residual control.

How should resistance be managed?

Rotate with other herbicide modes of action, combine chemical and non-chemical practices, and monitor surviving plants.

How can OEM customers customize this product?

Manufacturers can provide customized bottles, labels, cartons, private branding and technical documentation according to market requirements.

Conclusion

Prometryn 250g/L + S-Metolachlor 250g/L is a selective residual herbicide combination designed mainly for:

Pre-Emergence Annual Grass and Broadleaf Control

Its technical logic can be summarized as:

Prometryn → Photosynthesis Inhibition + Broadleaf Activity

S-Metolachlor → Seedling Growth Inhibition + Strong Annual Grass Activity

Together they provide:

Broad Spectrum Control + Residual Soil Protection + Early-Season Crop Protection

Successful performance depends on:

Correct Timing + Soil Moisture + Proper Placement + Registered Rate + Crop Safety + Resistance Management

For professional buyers, a reliable product should provide:

Correct 250 + 250g/L Specification + Stable Formulation + Batch Consistency + Regulatory Compliance + OEM Manufacturing Capability

Authoritative References

1. U.S. Environmental Protection Agency — S-Metolachlor EC Herbicide Label
   Official EPA label specifically listing S-Metolachlor + Prometryn tank mixtures for cotton, including preplant incorporated and preemergence applications and expanded target spectrum.

2. U.S. Environmental Protection Agency — Metolachlor / Prometryn Cotton Use Label
   Official label describing soil-specific use patterns, incorporation, crop-safety precautions and residual control principles.

3. U.S. Environmental Protection Agency — Prometryn 4L Registration Information
   EPA registration information documenting Prometryn uses in cotton and other crops and its activity against annual broadleaf plants and annual grasses.