Choosing between RM18 and RM43 can be a difficult decision for homeowners and landowners seeking effective vegetation control. Both products are powerful herbicides from the same manufacturer, but they serve different purposes and have distinct formulations. Understanding the differences between RM18 and RM43 is essential for selecting the right product for your specific weed control needs.

RM18 and RM43 are both non-selective herbicides designed for total vegetation control in areas where no plant growth is desired. However, they differ significantly in their active ingredients, concentration levels, and residual activity. RM43 contains a combination of glyphosate (43%) and imazapyr (0.7%), providing both contact kill and long-lasting residual control. RM18 contains glyphosate (18%) with no residual herbicide, making it a faster-degrading option for areas where you plan to plant in the near future.

Selecting the right herbicide between RM18 and RM43 depends on your specific needs, timeline, and the type of vegetation you need to control. If you need long-lasting bare-ground control with minimal reapplication, RM43 is the superior choice. If you need temporary vegetation control with the ability to plant again soon, RM18 is the better option. Understanding these differences ensures you choose the right product for your project.

This comprehensive guide examines the key differences between RM18 and RM43, comparing their active ingredients, application rates, residual activity, and ideal use cases. With the right information, you can confidently select the best herbicide for your vegetation control needs.

RM18 Vs RM43: Quick Comparison

Feature	RM18	RM43
Glyphosate Concentration	18%	43%
Imazapyr Concentration	None	0.7%
Residual Control	None (breaks down in soil)	Up to 12 months
Rainfast Period	2-4 hours	2 hours
Mixing Rate	4-6 oz per gallon	2.5-5 oz per gallon
Time to Kill	7-14 days	7-14 days
Soil Activity	No (breaks down quickly)	Yes (imazapyr persists)
Best For	Garden prep, lawn renovation	Fence lines, driveways, bare ground
Planting After Application	1-3 days	14-30 days (for sensitive plants)

RM18 Vs RM43: Detailed Comparison

1. Active Ingredients

The most significant difference between RM18 and RM43 is their active ingredient composition.

RM18 contains 18% glyphosate as its sole active ingredient. Glyphosate is a systemic herbicide that is absorbed through plant foliage and translocated to the roots. It works by inhibiting an essential enzyme (EPSP synthase) that plants need for growth, causing the plant to yellow and die over 7-14 days. Glyphosate breaks down quickly in the soil and has no residual activity, meaning it does not prevent future weed germination.

RM43 contains a powerful combination of 43% glyphosate and 0.7% imazapyr. The high glyphosate concentration provides fast, effective contact kill of existing vegetation. The imazapyr component provides long-lasting residual control, preventing weed regrowth for up to 12 months. This dual-action formulation makes RM43 significantly more potent and longer-lasting than RM18.

2. Residual Control

The presence or absence of residual control is perhaps the most important difference between these two products.

RM18 offers no residual control. The glyphosate breaks down in the soil within 1-3 days and is completely inactive within 7-14 days. This makes RM18 ideal for areas where you plan to plant new vegetation soon after treatment, as the herbicide will not harm new seedlings or transplants.

RM43 provides up to 12 months of residual control. The imazapyr component remains active in the soil, preventing weed seeds from germinating and establishing. This makes RM43 ideal for areas where you want long-lasting bare-ground control, such as fence lines, driveways, sidewalks, and other areas where no plant growth is desired.

3. Concentration And Mixing Rates

The different concentrations of these products affect how much you need to use.

RM18 contains 18% glyphosate, requiring a higher mixing rate. The standard application rate is 4-6 ounces of RM18 per gallon of water, depending on the target weeds. For tough weeds and brush, the higher rate (6 oz/gal) is recommended. For annual weeds and grasses, the lower rate (4 oz/gal) is sufficient.

RM43 contains 43% glyphosate, requiring a lower mixing rate. The standard application rate is 2.5-5 ounces of RM43 per gallon of water. For general weed control, 2.5 oz/gal is effective. For tough brush and woody plants, 5 oz/gal is recommended. The higher concentration means you use less product per gallon, making RM43 more cost-effective for large areas.

4. Rainfast Period

Both products have relatively short rainfast periods, but there is a slight difference.

RM18 requires 2-4 hours of drying time before rain. The lower concentration means slightly longer absorption time compared to RM43. Applying RM18 when rain is expected within 4 hours can reduce effectiveness.

RM43 requires only 2 hours of drying time before rain. The formulation includes surfactants that help the herbicide penetrate plant surfaces more quickly, reducing the rainfast period. This makes RM43 more forgiving in unpredictable weather conditions.

5. Planting After Application

The ability to plant after application is a critical consideration for many users.

RM18 allows planting 1-3 days after application. Since glyphosate breaks down quickly in soil and has no residual activity, it does not affect new seedlings or transplants. This makes RM18 ideal for garden preparation, lawn renovation, and other projects where you plan to plant soon after weed control.

RM43 requires a waiting period of 14-30 days before planting sensitive species. The imazapyr residual herbicide can affect new seedlings and transplants, particularly broadleaf plants and certain grasses. For less sensitive species, the waiting period may be shorter. Always check the label for specific planting recommendations.

6. Cost Comparison

Understanding the cost difference between these products helps with budget planning.

RM18 is generally less expensive per gallon but requires higher application rates. For small areas or one-time projects, RM18 may be more cost-effective. However, the lack of residual control means you may need to reapply more frequently.

RM43 is more expensive per gallon but requires lower application rates and provides long-lasting residual control. For large areas or long-term vegetation management, RM43 is more cost-effective due to reduced reapplication needs. The higher concentration also means you use less product overall.

When To Choose RM18

RM18 is the better choice when:

• You plan to plant soon: If you need to prepare a garden bed or renovate a lawn and plan to plant within days, RM18 is the right choice.
• You need temporary control: For areas where you only need temporary vegetation removal, RM18 provides effective control without long-term soil activity.
• You’re treating a small area: For small, one-time projects, RM18 is cost-effective and easy to use.
• You’re concerned about residual effects: If you want to avoid any potential impact on desirable plants, RM18 is the safer choice.
• You’re preparing a vegetable garden: RM18 is ideal for garden prep as it breaks down quickly and won’t affect your vegetables.

Best Products For RM18 Application

1. RM18 Weed Killer – Best Temporary Vegetation Control

RM18 is a powerful, fast-acting weed killer containing 18% glyphosate. This formulation provides effective control of annual and perennial weeds, grasses, and brush without leaving residual herbicide in the soil. The 18% glyphosate concentration is ideal for garden preparation, lawn renovation, and areas where you plan to plant soon.

RM18 breaks down quickly in the soil, allowing planting in as little as 1-3 days. The product is effective on a wide range of weeds and grasses, making it versatile for various applications. The affordable price makes it accessible for homeowners and small-scale projects.

Pros:

• No residual soil activity
• Plant in 1-3 days
• Fast-acting
• Effective on many weed types
• Affordable
• Versatile use
• Ideal for garden prep

Cons:

• No residual control
• Higher mixing rate
• Requires reapplication for long-term control

2. Sprayer For RM18 Application

A quality sprayer ensures even coverage and effective application of RM18. A backpack sprayer or pump sprayer with an adjustable nozzle provides control over the spray pattern and application rate. Choose equipment compatible with herbicide formulations.

For small areas, a 2-gallon pump sprayer is sufficient. For larger areas, a 4-gallon backpack sprayer provides extended capacity and reduces refill frequency. Look for sprayers with corrosion-resistant seals to handle herbicide formulations.

Pros:

• Even coverage
• Adjustable spray patterns
• Capacity for various area sizes
• Corrosion-resistant materials
• Durable construction
• Versatile application

Cons:

• Higher cost for quality models
• Requires cleaning after use
• May need calibration

When To Choose RM43

RM43 is the better choice when:

• You want long-term bare-ground control: For fence lines, driveways, sidewalks, and other areas where you want no vegetation for up to 12 months.
• You have large areas to treat: The higher concentration and lower mixing rate make RM43 more cost-effective for large properties.
• You want to reduce reapplication: The residual control means fewer applications over time, saving time and effort.
• You’re treating tough brush and woody plants: The 43% glyphosate concentration provides superior control of tough vegetation.
• You need weather-resistant application: The 2-hour rainfast period provides more flexibility in unpredictable weather.

Best Products For RM43 Application

3. RM43 Weed Killer – Best Long-Term Vegetation Control

RM43 is a professional-grade herbicide containing 43% glyphosate and 0.7% imazapyr. This powerful combination provides both contact kill and long-lasting residual control for up to 12 months. The high glyphosate concentration ensures effective control of existing vegetation, while the imazapyr prevents weed regrowth.

RM43 is ideal for fence lines, driveways, sidewalks, and other areas where no plant growth is desired. The long-lasting residual control reduces the need for frequent reapplication, saving time and money over the long term. The product is effective on a wide range of weeds, grasses, and brush.

Pros:

• 43% glyphosate concentration
• Up to 12 months residual control
• Fast-acting on existing weeds
• Effective on tough brush and woody plants
• 2-hour rainfast period
• Cost-effective for large areas
• Professional-grade formulation

Cons:

• Residual activity may affect desirable plants
• Waiting period before planting
• Requires careful handling

4. Marker Dye For RM43

Marker dye helps track where RM43 has been applied, reducing overlap and missed areas. Adding dye to the spray mixture provides a visual indication of coverage, ensuring thorough application. This is particularly useful for large areas where it is easy to lose track of sprayed areas.

Use a blue or green dye for visibility against various surfaces. The dye is temporary and will fade with sunlight or rain. It does not affect herbicide effectiveness.

Pros:

• Visual coverage tracking
• Reduces overlap
• Prevents missed areas
• Temporary color
• Inexpensive
• Improves application accuracy

Cons:

• Extra cost
• May stain clothing
• Requires mixing

RM18 Vs RM43: Which Should You Choose?

Choosing between RM18 and RM43 depends on your specific needs:

• Choose RM18 if: You need temporary weed control, plan to plant within days, are preparing a garden or lawn renovation, have a small area to treat, or want to avoid residual effects on desirable plants.
• Choose RM43 if: You need long-term bare-ground control, have large areas to treat, want to reduce reapplication frequency, are treating tough brush or woody plants, or need weather-resistant application timing.
• Consider the waiting period: RM18 allows planting in 1-3 days, while RM43 requires 14-30 days before planting sensitive species. Plan accordingly based on your timeline.
• Consider cost: While RM43 costs more per gallon, the lower application rate and reduced reapplication needs often make it more cost-effective for large areas.

Essential Tips For Using RM18 And RM43

• Read the label: Always read and follow the product label instructions for mixing rates, application methods, and safety precautions. The label contains essential information for effective and safe use.
• Apply during active growth: Both herbicides are most effective when applied to actively growing weeds. Apply when temperatures are between 60-85°F for optimal results.
• Check the weather: Apply when no rain is expected for at least 2 hours for RM43 and 4 hours for RM18. Wind speeds should be under 10 mph to prevent drift.
• Use proper equipment: Use a quality sprayer with a fan nozzle for even coverage. Clean equipment thoroughly after use to prevent corrosion.
• Add marker dye: Adding marker dye to the spray mixture helps track coverage and prevent missed areas.
• Protect desirable plants: Shield desirable plants from overspray to prevent damage. Use a shield or cover plants when spraying near them.
• Store properly: Store herbicides in their original containers in a cool, dry place away from children and pets. Do not transfer to unlabeled containers.

Frequently Asked Questions About RM18 Vs RM43

1. What is the difference between RM18 and RM43?

RM18 contains 18% glyphosate with no residual activity, while RM43 contains 43% glyphosate and 0.7% imazapyr, providing up to 12 months of residual control. RM18 is ideal for temporary control and planting soon, while RM43 is ideal for long-term bare-ground control.

2. Is RM43 stronger than RM18?

Yes, RM43 is significantly stronger than RM18. RM43 contains 43% glyphosate (compared to 18% in RM18) and includes imazapyr for residual control. This makes RM43 more potent and longer-lasting than RM18.

3. Can I mix RM18 and RM43 together?

No, you should not mix RM18 and RM43 together. Each product is formulated for specific uses, and mixing them could result in unpredictable results or waste. Choose the product that best suits your needs and use it as directed.

4. Which is better for killing brush and woody plants?

RM43 is better for killing brush and woody plants due to its 43% glyphosate concentration and the residual activity of imazapyr. The higher concentration provides better penetration of tough plant tissues, resulting in more effective control.

5. How soon can I plant after using RM18 vs RM43?

After using RM18, you can plant in 1-3 days. After using RM43, you should wait 14-30 days before planting sensitive species due to the residual activity of imazapyr. Always check the label for specific recommendations.

6. Does RM18 have residual control?

No, RM18 does not have residual control. It contains only glyphosate, which breaks down quickly in the soil and has no soil activity. This means it will not prevent new weeds from germinating.

7. Which product is more cost-effective?

For large areas or long-term control, RM43 is more cost-effective due to lower application rates and reduced reapplication needs. For small, one-time projects, RM18 may be more cost-effective upfront.

Conclusion

Choosing between RM18 and RM43 depends on your specific weed control needs, timeline, and long-term goals. RM18 is the superior choice for temporary vegetation control, garden preparation, and areas where you plan to plant soon. Its 18% glyphosate formulation provides effective control without residual soil activity, allowing planting in as little as 1-3 days.

RM43 is the better choice for long-term bare-ground control, large areas, and tough vegetation. Its powerful combination of 43% glyphosate and 0.7% imazapyr provides both contact kill and up to 12 months of residual control, reducing the need for frequent reapplication.

When making your decision, consider the size of your project, your timeline for planting, and your tolerance for reapplication. Both products are effective when used correctly, but they serve different purposes. With the right information and proper application techniques, you can choose the best herbicide for your specific needs.