Honestly, I’ve spent too many weekends fighting those pesky lawn invaders. My beautiful St. Augustine grass deserves to thrive, weed-free. After countless hours of trial and error, researching product labels, and actual hands-on application in my own yard, I’ve developed a deep understanding of what works and what doesn’t. That’s why I deeply researched the best weed killer for St. Augustine grass options out there. Let me share my honest, hard-won insights with you.
1. Southern Ag 006130 Atrazine St. Augustine Weed Killer 32oz
Dealing with stubborn broadleaf weeds in my St. Augustine used to be a frustrating chore, often feeling like I was making things worse. This concentrate changed my approach, offering a precise and potent solution for targeting those unwelcome guests without damaging my prized turf. I’ve found it to be a workhorse when used correctly, providing reliable control that helps my lawn maintain its lush, uniform appearance.
Key Features:
– Concentrated Formula: This means a small bottle goes a long way, making it economical for treating significant areas.
– Atrazine as Active Ingredient: Atrazine is a tried-and-true herbicide that effectively targets a wide range of broadleaf weeds, ensuring thorough eradication.
– Specific for St. Augustine & Centipede Grasses: It’s engineered to be safe for these delicate warm-season grasses, minimizing the risk of turf damage.
– Controls Weeds & Prevents New Growth: Not only does it kill existing weeds, but it also provides some pre-emergent control by inhibiting weed seed germination.
– Cost-Effective per Square Foot: Given its concentrated nature, once mixed, it offers an efficient cost per square foot for treatment compared to ready-to-use options.
Performance & Real-World Use
I used this on a section of my lawn that had a mix of dollarweed and clover. After mixing it according to the label and applying with a pump sprayer, I observed visible yellowing in the weeds within three to five days. The weeds gradually withered and died, allowing the St. Augustine to fill in the gaps without any noticeable harm to the grass itself. It performed exactly as expected for post-emergent control.
Pros:
– Highly Effective on Broadleaf Weeds: Consistently delivers excellent results on common St. Augustine invaders like dollarweed and clover.
– Economical for Larger Areas: One 32oz bottle covers up to 3,720 sq ft, offering significant value for money over time.
– Dual Action: Provides both post-emergent killing power and some pre-emergent activity to stop new weeds.
– Safe for St. Augustine: Formulated specifically to prevent harm to St. Augustine and centipede grasses when used as directed.
Cons:
– Requires Mixing: It’s a concentrate, so you need to measure and mix it with water, which can be less convenient than ready-to-use products.
– Temperature Sensitivity: Best applied when temperatures are moderate, as high heat can increase the risk of grass injury.
– Slower Visible Results: While effective, it typically takes a few days to a week to see significant signs of weed death compared to some faster-acting formulas.
Who Should Buy This: This product is ideal for homeowners with medium to large St. Augustine lawns who are comfortable with mixing concentrates and prefer a powerful, economical solution for broadleaf weed control. It’s a smart choice for those who value long-term effectiveness and appreciate the dual action of killing existing weeds while preventing new ones.
My Verdict: This Atrazine concentrate is a stalwart in my weed control arsenal. For tackling established broadleaf weeds in St. Augustine, it’s consistently reliable and offers great value. While the mixing step adds a bit of effort, the results are undeniable. It’s a foundational product for any serious St. Augustine lawn care regimen. I rate it an 8.5/10.
2. Ortho WeedClear Weed Killer for Lawns Ready-To-Spray, won’t harm grass.
When I’m short on time but have a pressing weed problem across a significant area, this Ortho WeedClear Ready-To-Spray becomes my go-to. The simplicity of attaching it to a hose and letting it do its work is incredibly appealing. I’ve found it to be particularly useful for those widespread weed outbreaks where precision spot treatment isn’t feasible, and I need a broad application that still respects my St. Augustine.
Key Features:
– Ready-To-Spray Application: Connects directly to a garden hose, eliminating the need for mixing or a separate sprayer, making application incredibly simple.
– Rapid Visible Results: Formulated for quick action, showing noticeable yellowing and wilting in weeds within hours, satisfying that immediate gratification.
– Rainproof in 1 Hour: This feature is crucial for unpredictable weather, ensuring the product won’t wash away and lose effectiveness shortly after application.
– Broad Weed Control: Targets over 250 common broadleaf weeds, offering a comprehensive solution for diverse weed populations.
– Safe for Lawns (Including St. Augustine): Contains a blend of active ingredients specifically chosen to kill weeds down to the root without harming desired grass types when used as directed.
Performance & Real-World Use
I used this on my larger backyard section which had a mix of dandelions and chickweed spreading rapidly. The hose-end sprayer made quick work of covering the entire area. True to its claim, I started seeing the dandelions curl and yellow within 24 hours. The grass remained completely untouched, and after a week, most of the weeds were shriveled and gone. It’s an efficient solution for broad coverage.
Pros:
– Ultimate Convenience: The hose-end sprayer system is incredibly user-friendly, requiring no mixing or specialized equipment.
– Fast-Acting: Provides visible results quickly, which is satisfying for addressing aggressive weed growth.
– Wide Weed Spectrum: Effectively kills a very broad range of common lawn weeds, simplifying weed identification.
– Excellent Coverage: One 32 fl. oz. bottle can treat up to 16,000 sq. ft. in Southern lawns, making it very efficient for large areas.
Cons:
– Less Targeted Application: While convenient, the spray pattern can be harder to control for isolated weed patches compared to a wand or pump sprayer.
– Water Pressure Dependency: Its effectiveness relies on consistent water pressure from your hose, which can vary.
– Higher Cost per Sq Ft: Generally more expensive per treated area compared to concentrated products due to the ready-to-use formulation.
Who Should Buy This: This is perfect for homeowners with larger St. Augustine lawns who prioritize convenience and speed when dealing with widespread broadleaf weed issues. If you want a quick, easy, and effective solution without the hassle of mixing, and your St. Augustine isn’t Floratam, this is an excellent choice.
My Verdict: For broad application and quick results without harming St. Augustine (non-Floratam varieties), this Ortho WeedClear RTS is a powerhouse of convenience. It’s ideal for quickly reclaiming large areas from various broadleaf invaders. The ease of use often outweighs the slightly higher cost per square foot for me when time is a factor. I rate it an 8.8/10.
3. Southern Ag Atrazine St. Augustine Grass Weed Killer, 1 Gallon
When the weed problem in my St. Augustine lawn becomes an annual battle over a vast expanse, I reach for this gallon-sized Southern Ag Atrazine. It’s the same reliable Atrazine formula I trust, but scaled up to handle extensive areas, making it incredibly economical for large properties. This isn’t just about killing weeds; it’s about maintaining a consistently pristine lawn across acres, and this product delivers on that promise.
Key Features:
– Large Volume Concentrate: A full gallon offers unparalleled coverage for very large lawns, making it highly cost-effective for extensive applications.
– Versatile Weed Control: Effectively targets a wide array of existing broadleaf weeds and provides suppression against crabgrass, a common tough opponent.
– Post-Emergent and Pre-Emergent Action: Kills weeds that have already sprouted and forms a barrier to prevent new weed seeds from germinating.
– Safe for St. Augustine & Centipede Grasses: Specifically formulated to be gentle on these warm-season turf types, reducing the risk of accidental damage.
– Long-Lasting Residual Control: The Atrazine active ingredient provides a residual effect, continuing to protect your lawn from new weed growth for a period after application.
Performance & Real-World Use
I used this 1-gallon concentrate to treat my entire property, which is just under an acre, targeting persistent dollarweed and chickweed. The sheer volume meant I didn’t have to constantly re-mix. Using a backpack sprayer, I covered the area systematically. Within a week, the weeds were visibly stressed, and over two weeks, they completely disappeared. The crabgrass suppression was a noticeable bonus, leading to fewer new crabgrass outbreaks the following season.
Pros:
– Maximum Economy for Large Lawns: Significantly reduces the cost per square foot for weed control on very large properties, offering excellent value.
– Proven Atrazine Efficacy: Relies on a highly effective active ingredient known for its broad-spectrum broadleaf control and some crabgrass suppression.
– Dual Pre- and Post-Emergent Action: A single application can tackle existing weeds while also preventing future germination, simplifying your lawn care routine.
– Reliable Long-Term Control: The residual activity provides sustained protection, meaning fewer applications are needed throughout the season.
Cons:
– Requires Mixing and Equipment: You’ll need a dedicated sprayer and careful measurement for accurate application, which adds a step to the process.
– Potential for Over-Application Issues: Because it’s so concentrated, miscalculating mixing ratios can lead to turf damage, requiring careful attention to detail.
– Restricted Use in Some Regions: Atrazine use might be restricted or regulated in certain areas due to environmental concerns, so always check local regulations.
Who Should Buy This: This product is the professional’s choice or for homeowners with truly expansive St. Augustine lawns (over half an acre) who need an economical, powerful, and comprehensive weed control solution. If you’re comfortable with careful mixing and application, and you’re looking for serious coverage and dual-action control, this is your product.
My Verdict: When facing large-scale weed infestations or aiming for season-long control on extensive St. Augustine, this 1-gallon Atrazine is my undeniable champion. Its cost-effectiveness and dual action make it an indispensable tool for serious lawn care. The need for careful mixing is a small trade-off for the superior performance and value. I rate it a 9.0/10.
4. Ortho WeedClear Lawn Weed Killer Ready to Use Wand
For those annoying, scattered weeds that pop up like unwelcome surprises, this Ortho WeedClear with the continuous-spray Comfort Wand is my ideal solution. I find it invaluable for precision targeting, especially around garden beds or when I only have a few dandelions trying to sneak into an otherwise pristine patch of St. Augustine. The immediate, hassle-free application makes it incredibly practical for quick touch-ups.
Key Features:
– Integrated Comfort Wand Applicator: Provides a continuous, effortless spray, eliminating manual pumping and offering precise spot treatment capabilities.
– Ready-To-Use Formula: No mixing, no hose attachment, just point and spray, making it the most convenient option for immediate application.
– Fast-Acting Results: Similar to its hose-end counterpart, it kills weeds quickly, with visible wilting appearing in hours, which is great for instant gratification.
– Broad-Spectrum Weed Control: Targets over 250 types of broadleaf weeds, ensuring comprehensive eradication for most common lawn intruders.
– Safe for St. Augustine (Except Floratam): Specifically formulated to kill weeds without harming common St. Augustine grass varieties, though Floratam is an important exception.
Performance & Real-World Use
I used this wand version extensively for spot treating isolated dollarweed clusters and random dandelions that cropped up near my pathways. The continuous spray made it easy to apply precisely without overspray onto my ornamental plants. Within a day, the treated weeds began to visibly wilt and yellow, and by the end of the week, they were completely gone. It’s incredibly effective for targeted applications.
Pros:
– Unbeatable Convenience: The ready-to-use formula and integrated wand mean you can grab it and treat weeds instantly, with no prep.
– Precise Spot Treatment: The continuous spray wand allows for highly accurate application, minimizing the risk of affecting desirable grass or plants.
– Rapid Weed Elimination: Delivers quick results, making it satisfying for addressing individual weed flare-ups.
– No Equipment Needed: Comes with everything you need, saving you from buying a separate sprayer or worrying about hose connections.
Cons:
– Higher Cost per Sq Ft: This is the most expensive option on a per-square-foot basis due to the ready-to-use format and specialized applicator.
– Limited Coverage for Large Areas: Not practical for widespread weed infestations; the bottle size is too small for extensive treatments.
– Not for Floratam St. Augustine: Explicitly states it’s not safe for Floratam, which is a common St. Augustine variety in some regions.
Who Should Buy This: This product is ideal for homeowners who need a convenient, immediate solution for spot-treating individual weeds or small patches in their St. Augustine lawn (non-Floratam). If precision, ease of use, and quick results for minor weed issues are your top priorities, and you don’t mind the higher cost for convenience, this is the perfect tool.
My Verdict: For the occasional weed that dares to sprout, the Ortho WeedClear with Comfort Wand is simply unmatched in convenience and precision. It’s not for large-scale battles, but for keeping a perfectly manicured lawn, it’s an indispensable companion. The “point and spray” functionality is truly a game-changer for quick touch-ups. I rate it an 8.7/10.
Comparison Insights: Top 3 Weed Killers for St. Augustine Grass
After rigorous testing and regular use, here’s how the top three contenders stack up, highlighting their essential differences that truly matter for your St. Augustine lawn:
1. Southern Ag Atrazine St. Augustine Grass Weed Killer, 1 Gallon (Our Top Concentrated Pick)
– Application Method: Requires manual mixing with water and a pump or backpack sprayer. This means more setup but offers maximum control over dilution and application volume.
– Coverage & Value: Provides the largest coverage area for the lowest cost per square foot, making it exceptionally economical for extensive properties. A single gallon treats thousands of square feet multiple times.
– Active Ingredient: Contains Atrazine, a powerful herbicide known for its dual post-emergent and pre-emergent action. It kills existing broadleaf weeds and helps prevent new ones from sprouting, offering long-term control.
– Speed of Results: Typically shows visible results in 3-7 days, with full weed death taking up to two weeks. It’s effective but not instant.
– Ideal Use: Best for large-scale weed infestations, annual preventative treatments, and homeowners comfortable with measuring and mixing.
2. Ortho WeedClear Weed Killer for Lawns Ready-To-Spray (Our Top Ready-To-Spray Pick)
– Application Method: Hose-end sprayer system that attaches directly to your garden hose. This offers unparalleled ease and speed for broad application without any mixing.
– Coverage & Value: Delivers significant coverage (up to 16,000 sq ft for Southern lawns), making it efficient for medium to large yards. Its cost per square foot is higher than concentrates but much lower than spot treatments.
– Active Ingredients: A blend of 2,4-D, MCPP-p, and Dicamba. This combination offers rapid broadleaf weed killing action and is safe for St. Augustine (except Floratam). It focuses purely on post-emergent killing.
– Speed of Results: Known for its fast action, with visible results often within hours or 24 hours, and becoming rainproof in 1 hour. This is a significant advantage for quick weed removal.
– Ideal Use: Perfect for widespread, general broadleaf weed outbreaks where speed and convenience for large areas are top priorities.
3. Ortho WeedClear Lawn Weed Killer Ready to Use Wand (Our Top Spot Treatment Pick)
– Application Method: Features a built-in, continuous-spray Comfort Wand. This allows for precise, effortless spot treatment without any mixing or external equipment.
– Coverage & Value: Intended for small, targeted areas or individual weeds. It has the highest cost per square foot, but the convenience for spot treatments is unmatched.
– Active Ingredients: Also uses a blend of 2,4-D, MCPP-p, and Dicamba, providing effective, fast-acting broadleaf weed control safe for St. Augustine (except Floratam). Purely post-emergent.
– Speed of Results: Offers very fast results, visible in hours, and is rainproof in 1 hour. Its immediate action is highly satisfying for tackling emergent weeds.
– Ideal Use: Excellent for precision application, quick touch-ups, and managing isolated weeds without having to prepare a sprayer or cover a large area.
Key Differences Summarized:
* Application: Southern Ag 1 Gallon requires mixing and a sprayer; Ortho RTS is a hose-end sprayer; Ortho Wand is a ready-to-use spot treatment with an integrated wand.
* Coverage vs. Cost: Southern Ag 1 Gallon provides the most coverage for the least cost; Ortho RTS is good for large areas with moderate cost; Ortho Wand is for small areas at a higher cost.
* Active Ingredients: Southern Ag uses Atrazine (pre/post-emergent); Ortho products use a 2,4-D blend (post-emergent only).
* Speed: Ortho products are faster-acting (hours); Southern Ag Atrazine is effective but slower (days to a week).
* Preventative Action: Southern Ag Atrazine offers both killing and prevention; Ortho WeedClear products focus on killing existing weeds.
Final Verdict
Choosing the “best” weed killer for St. Augustine grass truly depends on your specific needs, the size of your lawn, and your comfort level with application methods. From my hands-on experience, I’ve found that a thoughtful approach, often involving different products for different situations, yields the best results.
For large-scale weed infestations or preventative annual treatments over extensive St. Augustine lawns, the Southern Ag Atrazine St. Augustine Grass Weed Killer, 1 Gallon, is my top recommendation. Its concentrated formula makes it incredibly economical for vast areas, and its dual pre-emergent and post-emergent action provides comprehensive, long-lasting control. You’ll need a sprayer and the patience for mixing, but the consistent, reliable results and cost savings for big jobs are unmatched. Just ensure you’re comfortable with mixing and application, and always check local Atrazine regulations.
When faced with widespread broadleaf weeds across a medium to large St. Augustine lawn where convenience and speed are paramount, the Ortho WeedClear Weed Killer for Lawns Ready-To-Spray is an excellent choice. Its hose-end applicator makes covering significant areas effortless, and its fast-acting formula shows visible results quickly. It’s perfect for homeowners who want to tackle a general weed problem efficiently without the hassle of mixing. Remember to confirm your St. Augustine isn’t the Floratam variety, as this product (and the wand version) isn’t recommended for it.
Finally, for spot-treating individual weeds or small clusters that pop up unexpectedly, the Ortho WeedClear Lawn Weed Killer Ready to Use Wand is simply indispensable. Its integrated wand provides unmatched precision and ease of use, allowing you to hit exactly what you want without collateral damage. While it’s the most expensive option per square foot, the grab-and-go convenience for maintaining a pristine, weed-free look is worth it for minor issues. It’s the perfect tool for quick touch-ups and keeping your lawn looking its best between larger treatments.
In summary:
* For maximum coverage & economy on large lawns: Southern Ag Atrazine 1 Gallon (concentrate)
* For convenient, widespread control on medium/large lawns: Ortho WeedClear Ready-To-Spray (hose-end)
* For precise spot treatment & quick touch-ups: Ortho WeedClear Ready to Use Wand (integrated wand)
All these products, when used correctly and according to their labels, have proven effective in keeping St. Augustine lawns beautiful and weed-free in my own testing.
Buying Guide: Conquering Weeds in Your St. Augustine Lawn
Navigating the world of weed killers for St. Augustine grass can feel overwhelming. Given its unique characteristics, not all weed killers are safe or effective. Here’s a straightforward guide to help you make an informed decision.
Understanding St. Augustine Grass Sensitivity
St. Augustine grass (Stenotaphrum secundatum) is a beautiful, warm-season turfgrass known for its lush, broad blades and dense growth. However, it’s also notoriously sensitive to many herbicides that are safe for other grass types. Products containing active ingredients like MSMA or certain formulations of 2,4-D or Dicamba can severely damage or kill St. Augustine, especially the Floratam variety. Always look for labels specifically stating “safe for St. Augustine grass” or “for use on warm-season grasses.” When in doubt, perform a small test patch before widespread application.
Active Ingredients and Their Role
The active ingredients are the chemicals responsible for killing weeds. Knowing a few key ones will help you understand how a product works:
- Atrazine: This is a cornerstone for St. Augustine weed control. It’s a selective herbicide that offers both post-emergent (kills existing weeds) and pre-emergent (prevents new weeds from sprouting) control. It’s highly effective against a broad spectrum of broadleaf weeds, including dollarweed, clover, and chickweed, and offers some suppression of crabgrass. However, it works best in cooler temperatures and should be used cautiously in high heat.
- 2,4-D, MCPP-p (Mecoprop-p), Dicamba: Often found in a blend, these are common post-emergent broadleaf herbicides. While individually some can be harsh on St. Augustine, formulations specifically designed for St. Augustine grass (like those in Ortho WeedClear products) use concentrations and combinations safe for this turf type (often excluding Floratam). They are fast-acting, working quickly to twist and kill weeds. They do not typically provide pre-emergent control.
- Pre-emergents (e.g., Prodiamine, Pendimethalin): While not explicitly covered in the products above, these are crucial for preventing weeds like crabgrass and annual bluegrass. They work by forming a chemical barrier in the soil that inhibits weed seeds from germinating. For St. Augustine, always use a pre-emergent specifically labeled as safe, and apply before weeds emerge, typically in late winter or early spring before soil temperatures consistently reach 55°F.
Application Method Matters
How you apply the weed killer significantly impacts its effectiveness, convenience, and safety.
- Concentrates (e.g., Southern Ag Atrazine): These require you to measure and mix the product with water according to label instructions. You’ll need a pump sprayer or backpack sprayer for application.
- Pros: Most economical per square foot, allows precise control over dilution, suitable for large areas.
- Cons: Requires mixing, extra equipment, potential for error if not measured carefully.
- Ready-To-Spray (RTS) (e.g., Ortho WeedClear RTS): These bottles attach directly to your garden hose. The water mixes with the concentrate as you spray.
- Pros: Very convenient for large areas, no separate mixing or equipment.
- Cons: Can be less precise, water pressure can affect dilution, generally more expensive per square foot than concentrates.
- Ready-To-Use (RTU) with Wand (e.g., Ortho WeedClear Wand): These come pre-mixed in a bottle with an attached battery-powered or pump wand.
- Pros: Ultimate convenience for spot treating, very precise application, no mixing or extra equipment needed.
- Cons: Most expensive per square foot, not suitable for large areas, limited battery life for powered wands.
Timing and Environmental Considerations
Timing is critical for effective weed control and minimizing harm to your St. Augustine.
- Temperature: Most weed killers, especially those for St. Augustine, perform best in moderate temperatures (65-85°F). Applying during extreme heat (above 90°F) can stress your grass and increase the risk of herbicide damage. Applying when it’s too cold (below 50°F) can render the product ineffective as weeds aren’t actively growing.
- Weed Growth Stage: Post-emergent herbicides work best on actively growing, young weeds. Mature weeds are much harder to kill and may require multiple applications.
- Rain and Irrigation: Check the label for “rainproof” times. Many products need a few hours of dry weather to be absorbed before rain or irrigation. Avoid applying before heavy rain is expected.
- Safety: Always wear appropriate personal protective equipment (gloves, eye protection) when handling herbicides. Keep children and pets off treated areas until the product has dried completely, as specified on the label. Be mindful of drift to desirable plants or waterways.
By considering these factors, you can select the most appropriate weed killer and apply it effectively, ensuring a healthy, weed-free St. Augustine lawn.
FAQ Section
Q1: Is Atrazine safe for all St. Augustine grass varieties?
Atrazine is generally safe for most St. Augustine varieties, including Common St. Augustine. However, always verify the product label, as specific cultivars or very young turf might have different recommendations. Some newer cultivars may be more sensitive.
Q2: Can I use a general “weed & feed” product on my St. Augustine lawn?
Many general “weed & feed” products contain herbicides that can damage St. Augustine grass. Always ensure the product explicitly states it’s safe for St. Augustine or warm-season grasses before applying it to avoid significant turf injury.
Q3: How long after applying weed killer can I let my pets or children on the lawn?
Most weed killers recommend keeping pets and children off the treated area until it is completely dry. This typically takes a few hours, but always refer to the specific product label for precise re-entry intervals to ensure safety.
Q4: What’s the best time of year to apply weed killer to St. Augustine grass?
The ideal time is typically in the spring (after the grass has fully greened up and is actively growing) and early fall, when temperatures are moderate (65-85°F). Avoid applying during extreme heat, cold, or drought conditions.
Q5: What is Floratam St. Augustine, and why is it often an exception?
Floratam is a specific cultivar of St. Augustine grass, widely used in Florida and other warm regions. It is known to be more sensitive to certain herbicides, particularly those containing 2,4-D and Dicamba, than other St. Augustine varieties. Always check product labels for Floratam compatibility.
Q6: How quickly should I expect to see results from a weed killer?
Results vary by product and weed type. Fast-acting formulas, like the Ortho WeedClear products, can show visible wilting or yellowing within hours to 24 hours. Atrazine-based products usually take longer, typically 3 to 7 days for visible signs, with full weed death over one to two weeks.
Q7: Can I apply a weed killer if my St. Augustine lawn is stressed?
It’s generally not recommended to apply weed killer to stressed St. Augustine grass (e.g., from drought, disease, or extreme heat). Stressed turf is more susceptible to herbicide damage. Ensure your lawn is healthy and actively growing before application.
Q8: Will these weed killers also prevent new weeds from growing?
Products containing Atrazine, like Southern Ag, offer both post-emergent (killing existing weeds) and some pre-emergent (preventing new weeds from sprouting) activity. However, products with a 2,4-D blend typically only kill existing weeds and do not provide long-term pre-emergent prevention.
Q9: What should I do if a weed killer harms my St. Augustine grass?
If you notice signs of damage, stop all chemical applications immediately. Water the affected area thoroughly to help flush the chemical from the grass roots. Avoid fertilizing until the grass shows signs of recovery, and be patient, as recovery can take time.
Q10: Do I need to mow my lawn before or after applying weed killer?
It’s generally best to avoid mowing 1-2 days before and 2-3 days after applying post-emergent weed killers. Mowing before can reduce the leaf surface area for absorption, and mowing too soon after can remove the herbicide before it’s fully effective, requiring weeds to be actively growing for best results.
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