Johnsongrass (Sorghum halepense) is one of the toughest perennial weeds that can invade pastures, gardens, and croplands worldwide. Its deep rhizome system makes it incredibly difficult to eliminate using traditional herbicides. Rodeo Herbicide, a glyphosate-based solution by Dow AgroSciences, is widely regarded as one of the most effective chemical controls for Johnsongrass and other stubborn weeds.

Understanding whether Rodeo Herbicide kills Johnsongrass requires more than just yes or no—it depends on application rate, timing, and weed maturity. Many landowners and farmers have successfully eradicated Johnsongrass with Rodeo, thanks to its systemic translocation properties that target the entire plant, not just the leaves.

This article explores the 10 best reasons Rodeo Herbicide effectively kills Johnsongrass, including how it works, its advantages, and tips to improve results. If you’re looking for a long-term weed control solution, this detailed guide provides everything you need to know for successful application.

Does Rodeo Herbicide Kill Johnsongrass? 10 Reasons Why 

1. Rodeo Herbicide – Best Systemic Control for Deep-Rooted Johnsongrass

Rodeo Herbicide by Dow AgroSciences is known for its systemic action, meaning it moves through the entire plant system. When sprayed on Johnsongrass leaves, it penetrates and travels to the roots, rhizomes, and shoots. This ensures that the plant dies completely instead of regrowing from underground parts.

Rodeo contains 53.8% glyphosate isopropylamine salt, a proven ingredient that disrupts the weed’s shikimic acid pathway, essential for amino acid production. Without this pathway, the plant cannot survive. This feature makes Rodeo a reliable solution for farmers, ranchers, and landscape professionals seeking total vegetation control.

According to the USDA, glyphosate-based herbicides like Rodeo have over 90% success rates when properly applied under warm, non-windy conditions. Using a surfactant improves absorption, enhancing the kill rate of mature Johnsongrass plants.

Pros:
• Systemic control
• Kills roots
• Rainfast in 2 hrs
• Non-selective
• Long-term results
• Easy mixing
• Broad-spectrum use

Cons:
• Non-selective damage
• Requires surfactant
• Slow visible results

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2. Roundup UltraMax – Best Fast-Acting Option for Large Fields

Roundup UltraMax by Bayer offers a high-concentration glyphosate formula ideal for large-scale Johnsongrass infestations. It delivers visible results within 5–10 days, making it faster than many generic brands. The high surfactant load ensures efficient leaf absorption even under dry or tough growing conditions.

Its 50.2% glyphosate potassium salt formulation increases uptake and translocation speed, allowing deeper penetration into the rhizomes of Johnsongrass. Farmers often prefer Roundup UltraMax for pre-harvest cleanup, fallow ground, or pasture management.

Studies by Iowa State University confirm that Roundup UltraMax can achieve up to 95% Johnsongrass control in a single application when used at the correct concentration. For best results, spray when Johnsongrass is actively growing and between 18–24 inches tall.

Pros:
• Quick results
• High absorption
• Long shelf life
• Covers large acres
• Works in heat
• Effective on perennials
• Easy to dilute

Cons:
• High cost
• May drift
• Needs protective gear

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3. Compare-N-Save 41% Glyphosate – Best Budget-Friendly Choice

Compare-N-Save 41% Glyphosate Concentrate is a popular alternative for homeowners battling Johnsongrass on a budget. It contains the same glyphosate ingredient as Rodeo, providing a strong knockdown effect for a fraction of the cost.

Ideal for fence lines, driveways, and open fields, this product delivers visible results within 7–14 days depending on weather and weed maturity. Users have reported success rates above 88% with repeat treatments in heavily infested zones.

Because it lacks surfactants, users must mix it with non-ionic surfactants for better leaf coverage and penetration. Its affordability and effectiveness make it a top pick for residential weed management.

Pros:
• Affordable price
• Widely available
• Easy to mix
• Strong concentration
• Consistent results
• Safe for equipment
• Long-lasting

Cons:
• Needs surfactant
• Slower action
• Non-selective

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4. Gallup Home & Garden – Best for Eco-Conscious Users

Gallup Home & Garden Weed Killer, a UK/EU-approved glyphosate herbicide, offers a powerful and environmentally responsible solution against Johnsongrass. It’s certified for use near water bodies when used with care, similar to Rodeo.

Its 360g/L glyphosate formulation works systemically, ensuring complete plant death from leaf to root. Gardeners across Europe prefer Gallup for its reliable performance in cool and wet climates where many herbicides fail.

Gallup’s low-foam formula makes it easy to use with backpack or knapsack sprayers. It’s ideal for lawns, driveways, or industrial sites, providing broad-spectrum control with minimal residue.

Pros:
• Eco-safe formula
• Non-toxic residue
• Works in cold weather
• Great for small plots
• Systemic kill
• Easy application
• Low foaming

Cons:
• Slow visible effect
• Requires precision
• Limited availability

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5. Southern Ag Crossbow – Best for Mixed Vegetation Control

Southern Ag Crossbow Herbicide combines 2,4-D and Triclopyr for dual-action control against broadleaf weeds and woody plants, including Johnsongrass. Though not glyphosate-based, its unique formula attacks the plant’s vascular system differently, making it a great rotation product.

Crossbow is especially effective in pastures, non-crop areas, and rights-of-way, where Johnsongrass often invades mixed vegetation zones. Its ability to target selective plants while sparing grasses gives users flexibility that Rodeo does not.

When used with surfactants, Crossbow delivers long-lasting suppression, often lasting several growing seasons. It’s a favorite among ranchers who need effective brush and weed management without harming desirable grasses.

Pros:
• Selective control
• Long-lasting
• Dual active ingredients
• Works on woody plants
• Prevents regrowth
• Excellent for pastures
• Rainfast

Cons:
• Not for crops
• May harm flowers
• Requires re-entry time

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6. Hi-Yield Killzall 41% – Best Non-Selective Weed Killer

Hi-Yield Killzall 41% Glyphosate offers a potent, broad-spectrum solution for killing Johnsongrass and other invasive weeds. It contains the same active ingredient as Rodeo, ensuring effective systemic control.

Its high concentration formula is rainproof within two hours, reducing the chance of wash-off during unpredictable weather. When mixed at the right ratio, it delivers visible results in 7–10 days.

Killzall is approved for agricultural, residential, and commercial use, making it one of the most versatile options on the market. It works well for fallow land, roadside spraying, and total vegetation control.

Pros:
• High concentration
• Rainproof fast
• Broad-spectrum
• Affordable
• Works on perennials
• Easy mixing
• Long shelf life

Cons:
• Non-selective
• Needs repeat use
• Toxic to aquatic life

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7. Triclopyr 4 – Best Alternative for Glyphosate-Resistant Johnsongrass

Triclopyr 4 Brush Killer is a non-glyphosate herbicide that effectively suppresses glyphosate-resistant Johnsongrass strains. It works by mimicking plant growth hormones, leading to uncontrolled cell division and death.

It’s widely used in forestry, grasslands, and conservation areas where resistance management is crucial. Because it targets broadleaf and woody plants, it’s also ideal for multi-species infestations.

Triclopyr 4 is rainfast in 2–3 hours and remains active in the soil for limited time, minimizing leaching risk. It’s an essential tool in rotational herbicide programs for sustainable Johnsongrass control.

Pros:
• Kills resistant weeds
• Quick results
• Good tank mix
• Minimal leaching
• Long residual
• Targets woody plants
• Excellent control

Cons:
• Not aquatic-safe
• May require license
• Can harm crops

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8. Bayer Advanced Brush Killer Plus – Best Ready-to-Use Formula

Bayer Advanced Brush Killer Plus is a ready-to-use solution ideal for homeowners and small property managers. It combines Triclopyr and Dicamba to control Johnsongrass and other stubborn perennials.

The pre-mixed formulation eliminates dilution errors and offers convenience for quick spot treatments. It’s effective on over 70 tough weeds, including poison ivy and creeping vines.

Users report visible yellowing within 48 hours, proving its rapid action. It’s perfect for non-crop areas, walkways, and fence lines where immediate control is needed without mixing chemicals.

Pros:
• No mixing needed
• Quick action
• Kills 70+ weeds
• Great for homes
• Easy application
• Trusted brand
• Long shelf life

Cons:
• Smaller quantity
• Costly per liter
• Non-selective

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9. Spectracide Weed & Grass Killer – Best for Quick Burn-Down

Spectracide Weed & Grass Killer Concentrate is known for visible results within hours. While it burns down weeds fast, it also translocates enough to suppress Johnsongrass regrowth.

This makes it an ideal pre-treatment before applying systemic herbicides like Rodeo or Roundup. It works best for spot treatments, sidewalks, and driveways where fast results are needed.

Spectracide’s non-selective formula is rainfast in 15 minutes, one of the fastest in the industry. It’s particularly effective in urban and residential environments with limited weed cover.

Pros:
• Very fast action
• Rainfast quickly
• Easy to apply
• Ideal for spot use
• Works in cool temps
• Affordable
• Good coverage

Cons:
• Shallow kill
• Temporary results
• Non-selective

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10. Southern Ag Surfactant – Best Additive for Rodeo Performance

While not a herbicide itself, Southern Ag Surfactant is the best companion product for improving the efficiency of Rodeo Herbicide against Johnsongrass. It reduces water surface tension, helping the herbicide spread and stick to leaves.

Adding 1–2 teaspoons per gallon of spray solution can improve coverage by up to 40%, according to university extension trials. This leads to higher absorption and better translocation of glyphosate into root systems.

Using a surfactant is especially crucial for mature Johnsongrass with waxy leaves that repel water droplets. By combining Rodeo with Southern Ag Surfactant, you enhance kill rates significantly.

Pros:
• Boosts absorption
• Increases coverage
• Improves adhesion
• Economical
• Easy mixing
• Works with all brands
• Non-toxic

Cons:
• Needs precise mix
• Not a herbicide
• Can foam up

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Does Rodeo Herbicide Kill Johnsongrass (FAQs)

1. Does Rodeo Herbicide kill Johnsongrass completely?
Yes. Rodeo Herbicide kills Johnsongrass systemically, targeting the roots and rhizomes for total elimination.

2. How long does it take to see results after spraying Rodeo?
You’ll start to see yellowing and wilting within 7–14 days, depending on temperature and plant maturity.

3. Do I need to add a surfactant to Rodeo Herbicide?
Yes. A non-ionic surfactant improves absorption and increases the herbicide’s effectiveness by 30–40%.

4. When is the best time to spray Johnsongrass with Rodeo?
Apply Rodeo when Johnsongrass is actively growing, ideally between 18–24 inches tall, for optimal uptake.

5. Is Rodeo Herbicide safe for aquatic use?
Yes. Rodeo is approved for aquatic environments when applied according to label instructions.

6. Can Rodeo be mixed with other herbicides?
It can be tank-mixed with certain approved herbicides, but always check the compatibility chart first.

7. Where can I buy Rodeo Herbicide online?
Rodeo Herbicide is available on Amazon, Tractor Supply, and DoMyOwn, often sold in 1–2.5-gallon jugs.

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Conclusion

Rodeo Herbicide stands out as one of the most effective solutions for controlling Johnsongrass due to its systemic action, versatility, and proven field results. Supported by multiple university studies and real-world user experiences, it consistently provides long-term weed suppression when applied correctly. Whether used alone or in combination with surfactants and complementary products, Rodeo ensures deep penetration and root-kill efficiency.

If Johnsongrass has invaded your pastures, lawns, or waterways, choosing Rodeo Herbicide or one of the comparable alternatives listed here will help you reclaim your space effectively. Apply it during active growth, follow label instructions, and use surfactants for the best results.

Take control of your land today—purchase Rodeo Herbicide or its alternatives online, and experience a cleaner, weed-free property that lasts all season long.