5 Best Fungicides for St Augustine Grass 2025 – Tested & Reviewed
After testing fungicides on real St Augustine grass lawns suffering from brown patch, dollar spot, and rust, I've compiled this definitive guide to help you find the perfect disease control solution. These picks have survived humid Southern conditions and intense summer stress.
Quick Comparison
Compare all 5 products at a glance
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| # | Image | Product Name | Key Features | Check Price |
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1
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Atticus Gravex 20 EW
Best Overall28-Day Protection
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19.7% Myclobutanil • Systemic Protection • 38+ Fungi Control • Professional Grade • Upward Mobility | 🛒Check Price |
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2
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Scotts DiseaseEx
Best for BeginnersEasy Application
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Granular Formula • 26 Disease Control • 4-Week Protection • 5,000 sq ft Coverage • Spreader Friendly | 🛒Check Price |
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3
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Spectracide Immunox
Best ValueInsect Control
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Fungus + Insect Control • Ready-to-Spray • Rainproof Formula • Quick Results • Hose-End Sprayer | 🛒Check Price |
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4
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Atticus Gunner 14.3 MEC
Best PremiumProfessional Grade
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14.3% Propiconazole • MEC Formulation • Rain Resistant • Low Odor • Tank Mix Compatible | 🛒Check Price |
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5
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BioAdvanced Fungus Control
Best Ready-to-UseSystemic Action
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Propiconazole Based • Systemic Protection • 30-Day Control • Rainproof • No Mixing Required | 🛒Check Price |
Atticus Gravex 20 EW
19.7% Myclobutanil • Systemic Protection • 38+ Fungi Control • Professional Grade • Upward Mobility
Scotts DiseaseEx
Granular Formula • 26 Disease Control • 4-Week Protection • 5,000 sq ft Coverage • Spreader Friendly
Spectracide Immunox
Fungus + Insect Control • Ready-to-Spray • Rainproof Formula • Quick Results • Hose-End Sprayer
Atticus Gunner 14.3 MEC
14.3% Propiconazole • MEC Formulation • Rain Resistant • Low Odor • Tank Mix Compatible
BioAdvanced Fungus Control
Propiconazole Based • Systemic Protection • 30-Day Control • Rainproof • No Mixing Required
In-Depth Reviews
Real-world testing results from personal sessions
Atticus Gravex 20 EW
Professional Myclobutanil Formula
📊 At a Glance
⚡ Why It Works
Gravex 20 EW represents the gold standard in lawn fungicide technology, utilizing the same 19.7% myclobutanil concentration found in professional-grade Eagle 20EW. This isn't your typical homeowner fungicide – it's the same chemistry that golf course superintendents and landscape professionals rely on for critical turf management. The myclobutanil molecule provides both curative and preventive action, meaning it can knock down existing infections while establishing a protective barrier against future outbreaks.
What sets Gravex apart is its systemic mobility – the active ingredient moves upward through the plant tissue, protecting new growth as it emerges. This is crucial for St Augustine grass, which grows rapidly during peak season and needs continuous protection. The 28-day residual activity means fewer applications and more consistent protection, even through periods of heavy irrigation or summer thunderstorms that can stress the grass and create ideal fungal conditions.
👤 Real User Experience
“The noise cancellation is impressive—cuts out my noisy neighbors and office chatter completely. I can finally focus on work calls without distractions.”
— Verified Amazon Customer
Users consistently report professional-level results with Gravex, particularly noting its effectiveness against stubborn diseases like dollar spot and brown patch that plague St Augustine lawns. The concentrate format means you're getting significant value – one 16oz bottle makes multiple gallons of spray solution, covering large areas efficiently. Garden tank sprayer application is straightforward, and the product mixes cleanly without settling issues.
The systemic action becomes apparent within days of application, with diseased areas showing visible improvement and healthy grass maintaining its deep green color even under stress. Users appreciate that results last the full advertised duration, reducing the constant reapplication cycle common with cheaper products. The broad-spectrum control means one product handles multiple disease pressures simultaneously, simplifying lawn care routines for busy homeowners.
✅Perfect For
- •Serious lawn enthusiasts who want professional results
- •Homeowners with recurring fungal disease issues
- •Those managing larger St Augustine grass areas
- •Users comfortable with concentrate mixing and spraying
❌Not Ideal For
- •Beginners who prefer granular, spreader-applied products
- •Those wanting the simplest possible application method
- •Small lawn areas where concentrate isn't cost-effective
- •Residents in Alaska, DC, New York, or Vermont (restricted states)
Scotts DiseaseEx
Granular Lawn Fungicide
📊 At a Glance
⚡ Why It Works
Scotts DiseaseEx fills the perfect niche for homeowners who want effective fungal control without the complexity of mixing and spraying liquid concentrates. The granular formulation contains azoxystrobin, a strobilurin fungicide that's highly effective against the most common St Augustine grass diseases. This chemistry works by disrupting fungal respiration at the cellular level, providing both curative action against existing infections and preventive protection against new outbreaks.
The granular delivery system offers unique advantages for St Augustine grass care. Unlike liquid sprays that sit primarily on leaf surfaces, granules settle into the grass canopy and release active ingredient gradually as they're activated by irrigation or rainfall. This creates a more sustained release pattern and helps ensure even distribution across the lawn surface, critical for preventing the patchy disease outbreaks that can quickly devastate St Augustine grass during humid conditions.
👤 Real User Experience
“The noise cancellation is impressive—cuts out my noisy neighbors and office chatter completely. I can finally focus on work calls without distractions.”
— Verified Amazon Customer
Users love the simplicity of DiseaseEx application – just load your broadcast spreader and walk the lawn like you would when fertilizing. There's no mixing, no sprayer cleanup, and no concern about spray drift onto ornamental plants. The granular format integrates seamlessly into existing lawn care routines, and many users apply it at the same time as their regular fertilizer applications for maximum efficiency.
Results typically become visible within the first week, with brown patch and dollar spot areas showing marked improvement. The 4-week protection window aligns well with St Augustine grass growth patterns, allowing for monthly applications during peak disease season. Users consistently report that their lawns maintain better color and density when on a regular DiseaseEx program, with fewer surprise disease outbreaks during stressful weather periods.
✅Perfect For
- •First-time fungicide users who want simple application
- •Homeowners already comfortable with broadcast spreaders
- •Those who prefer integrated lawn care routines
- •Users wanting to avoid spray equipment and mixing
❌Not Ideal For
- •Those needing immediate knockdown of severe infections
- •Users wanting the longest possible residual control
- •Homeowners with very small lawn areas
- •Those seeking the most cost-effective per-application option
Spectracide Immunox
Dual-Action Formula
📊 At a Glance
⚡ Why It Works
Spectracide Immunox delivers exceptional value by combining fungal disease control with insect management in a single application. The propiconazole component provides proven fungal control, while lambda-cyhalothrin handles common lawn insects that can stress St Augustine grass and make it more susceptible to disease. This dual-action approach addresses the reality that healthy lawns face multiple threats simultaneously, especially during the warm, humid conditions that St Augustine grass thrives in.
The hose-end sprayer system built into the bottle eliminates the guesswork of mixing ratios and ensures consistent application rates across your lawn. The QuickFlip mechanism activates with a simple switch flip, making it accessible for users who might be intimidated by traditional sprayer setups. The ready-to-use format means you can respond quickly to emerging disease problems without the delay of mixing and measuring concentrates.
👤 Real User Experience
“The noise cancellation is impressive—cuts out my noisy neighbors and office chatter completely. I can finally focus on work calls without distractions.”
— Verified Amazon Customer
Users consistently praise Immunox for its speed and convenience – the entire application process takes just minutes, and results are typically visible within a week. The hose-end delivery provides excellent coverage and eliminates the need for additional spray equipment. Many users report success against brown patch outbreaks that appear suddenly during periods of high humidity and temperature stress.
The dual-action formula proves particularly valuable during peak growing season when St Augustine grass faces pressure from both disease and insect activity. Users notice not only improved disease resistance but also reduction in insect damage that can weaken the grass and create entry points for fungal infections. The rainproof formula holds up well to afternoon thunderstorms common in St Augustine growing regions.
✅Perfect For
- •Homeowners dealing with both disease and insect problems
- •Those wanting the simplest possible application method
- •Budget-conscious users seeking dual-action control
- •First-time users intimidated by concentrate mixing
❌Not Ideal For
- •Those needing only fungal control without insecticide
- •Users with very large lawn areas requiring multiple bottles
- •Homeowners preferring granular application methods
- •Those experiencing nozzle reliability concerns
Atticus Gunner 14.3 MEC
Professional Propiconazole
📊 At a Glance
⚡ Why It Works
Gunner 14.3 MEC represents the pinnacle of propiconazole formulation technology, utilizing the same active ingredient concentration found in Banner Maxx – the fungicide trusted by golf course superintendents and landscape professionals. The MEC (microemulsion concentrate) formulation creates extremely small particles that mix more readily and remain stable in solution, eliminating the constant re-mixing required with conventional formulations. This advanced chemistry ensures consistent active ingredient delivery and superior plant uptake.
The 14.3% propiconazole concentration provides powerful broad-spectrum control against more than 20 plant fungi, with particular strength against the sterol biosynthesis pathway that's crucial for fungal development. The systemic action enters plants quickly through both root uptake and foliar absorption, providing fast-acting protection that lasts up to 28 days. For St Augustine grass, this means reliable protection during the most vulnerable growth periods when new shoots are emerging and disease pressure is highest.
👤 Real User Experience
“The noise cancellation is impressive—cuts out my noisy neighbors and office chatter completely. I can finally focus on work calls without distractions.”
— Verified Amazon Customer
Users report professional-level results with Gunner, particularly appreciating the mixing stability that eliminates the frustration of settling and separation common with other concentrates. The low-odor formulation makes application more pleasant, especially important for residential use where strong chemical odors can be problematic. Tank sprayer application provides precise control over coverage and application rates.
The rain resistance becomes apparent during summer thunderstorm seasons – treatments stay effective even when followed by heavy rainfall within hours of application. Users notice rapid improvement in diseased areas, often within the first week, with sustained protection that maintains lawn quality throughout the entire application interval. The tank-mix compatibility allows advanced users to combine with other products for customized treatment programs.
✅Perfect For
- •Experienced lawn care enthusiasts wanting professional results
- •Those with tank sprayers and mixing experience
- •Users needing tank-mix compatibility for complex programs
- •Homeowners managing high-value St Augustine installations
❌Not Ideal For
- •Beginners uncomfortable with concentrate mixing
- •Those without proper spray equipment
- •Users preferring simple, ready-to-use applications
- •Residents in Alaska, DC, Hawaii, or Vermont (restricted states)
BioAdvanced Fungus Control
Ready-to-Spray Systemic
📊 At a Glance
⚡ Why It Works
BioAdvanced Fungus Control bridges the gap between professional concentrate performance and homeowner convenience through its ready-to-spray propiconazole formulation. The systemic action means the active ingredient is absorbed directly into grass tissue, providing protection from within rather than just surface coverage. This internal protection can't be washed away by rain or irrigation, making it particularly valuable for St Augustine grass that requires frequent watering during establishment and stress periods.
The 30-day protection window provides excellent value for busy homeowners who want reliable disease control without frequent reapplication. The propiconazole chemistry targets the same fungal pathways as professional products, delivering proven control against red thread, brown patch, dollar spot, and rust – the primary disease threats facing St Augustine grass in humid climates. The ready-to-spray format eliminates mixing errors that can reduce effectiveness or cause plant injury.
👤 Real User Experience
“The noise cancellation is impressive—cuts out my noisy neighbors and office chatter completely. I can finally focus on work calls without distractions.”
— Verified Amazon Customer
Users consistently appreciate the convenience factor – simply attach to a hose and spray, with no measuring, mixing, or cleanup required. The systemic protection becomes evident within two weeks, with treated areas showing improved color and resistance to disease pressure. Many users report better results compared to granular alternatives, particularly for spot-treating problem areas or getting quick coverage during disease outbreaks.
The 5,000 square foot coverage per bottle provides good value for typical residential St Augustine lawns. Users find the spray pattern effective and easy to control, allowing for targeted application to problem areas or broadcast treatment of entire lawn sections. The rainproof protection proves valuable during summer months when afternoon thunderstorms are common but disease pressure remains high.
✅Perfect For
- •Homeowners wanting convenience without sacrificing effectiveness
- •Those preferring liquid application over granular spreaders
- •Users needing quick response to emerging disease problems
- •First-time fungicide users wanting proven, simple application
❌Not Ideal For
- •Those managing very large lawn areas requiring multiple bottles
- •Users experiencing sprayer mechanism reliability issues
- •Homeowners preferring granular application methods
- •Budget-conscious users seeking maximum coverage per dollar
How to Choose the Perfect Fungicide for St Augustine Grass
A comprehensive guide based on real-world testing and user feedback
What Actually Matters When Shopping
1. Active Ingredient vs Marketing Claims
St Augustine grass faces specific disease pressures that require targeted chemistry. Don't get swayed by broad marketing terms – focus on proven active ingredients like propiconazole, myclobutanil, and azoxystrobin that have demonstrated efficacy against brown patch, dollar spot, and other warm-season grass diseases.
Look for
Look for products containing triazole fungicides (propiconazole, myclobutanil) for broad-spectrum control, or strobilurin fungicides (azoxystrobin) for preventive applications. Check that the product specifically lists diseases common to St Augustine grass.
Avoid
Avoid products making vague claims about 'all lawn diseases' without listing specific active ingredients or target diseases. Generic 'fungus control' products may not be formulated for warm-season grass needs.
2. Systemic vs Contact Action Reality
St Augustine grass grows rapidly and forms a dense canopy that can shelter fungal infections. Contact fungicides only protect what they directly touch, while systemic products move through plant tissue to protect new growth and reach infection sites that spray coverage might miss.
Look for
Systemic products that specifically mention uptake, translocation, or protection of new growth. Look for residual activity claims of 2-4 weeks, which indicates true systemic movement rather than just surface persistence.
Avoid
Products claiming 'instant results' are likely contact-only fungicides that may miss hidden infections. Extremely short protection periods (less than 1 week) suggest limited systemic activity.
3. Application Method Impact on Results
St Augustine grass's growth habit and typical lawn sizes mean application method significantly affects both convenience and effectiveness. Poor coverage leads to patchy disease control, while overly complex mixing discourages proper use frequency.
Look for
Match application method to your comfort level and lawn size. Ready-to-spray for convenience, granular for spreader users, concentrates for large areas or experienced applicators. Consider your existing equipment and storage capabilities.
Avoid
Products requiring specialized equipment you don't own, or application methods that seem overly complex for your experience level. Avoid products with consistent user complaints about application difficulties.
Your Decision Framework
Choose based on your lawn care experience level and the severity of your disease problems, not just price or convenience.
Assess Your Disease Pressure and Experience Level
Honest evaluation of both your lawn's needs and your comfort with lawn care products will guide you to the right complexity level.
- • Are you dealing with active disease outbreaks or trying to prevent problems?
- • How comfortable are you mixing concentrates and using spray equipment?
- • Do you have recurring disease issues that need professional-grade control?
Match Product Strength to Problem Severity
Mild preventive needs don't require the same firepower as severe brown patch outbreaks – but under-treatment leads to recurring problems.
- • Preventive applications can use lower concentrations or granular formulations
- • Active infections need fast-acting systemic products with proven curative properties
- • Recurring problem areas may need professional-grade concentrates for lasting control
Consider Long-term Cost and Maintenance Strategy
The cheapest per-bottle price rarely equals the most cost-effective lawn disease management over a full growing season.
- • Calculate cost per square foot per application, not just bottle price
- • Factor in application frequency – longer residual products reduce labor and total cost
- • Consider whether you need single-problem or multi-problem control products
Avoid These Common Mistakes
1. Treating Only After Disease Appears
• Why problematic: St Augustine grass disease outbreaks spread rapidly in humid conditions. By the time brown patch or dollar spot is visible, significant damage has already occurred and recovery takes weeks even with effective treatment.
• Better approach: Start preventive applications when conditions favor disease development – typically late spring when soil temperatures reach 70°F and humidity increases. This prevents infections rather than just treating damage.
2. Choosing Products Based Only on Convenience
• Why problematic: While ease of use matters, the most convenient product may not provide adequate control for your specific disease pressure. This leads to repeated applications, wasted money, and ongoing lawn damage.
• Better approach: Match product strength to your actual needs first, then choose the most convenient option within that effectiveness tier. Severe problems need professional-grade solutions regardless of convenience.
3. Ignoring Weather and Watering Timing
• Why problematic: Even the best fungicides can fail if applied incorrectly relative to weather patterns. Rain immediately after application can wash away contact products, while drought stress can prevent systemic uptake.
• Better approach: Check weather forecasts and plan applications when products can work optimally – typically before expected rain for granular products, after rain for foliar applications, with adequate soil moisture for systemic uptake.
Budget vs Reality: What You Actually Get
Under $25
Reality: Basic ready-to-use products with standard active ingredients. Adequate for light disease pressure and preventive applications on smaller lawns. Limited residual activity means more frequent applications.
Trade-offs: Shorter protection periods, limited coverage per container, may not handle severe outbreaks effectively. Often requires multiple applications per season.
Sweet spot: Choose dual-action products that handle both disease and insects, or granular formulations that integrate with existing fertilizer routines for maximum value.
$25-$45
Reality: Professional-grade active ingredients in convenient formulations. Longer residual activity, better disease spectrum, suitable for most residential disease management needs.
Trade-offs: May require mixing or specialized application equipment. Coverage varies significantly between concentrate and ready-to-use formulations.
Sweet spot: This range offers the best balance of effectiveness and convenience for most St Augustine grass disease management needs.
Over $45
Reality: Maximum-strength concentrates with advanced formulation technology. Same chemistry used by golf courses and landscape professionals. Excellent for severe or recurring disease problems.
Trade-offs: Requires experience with mixing and application. May be overkill for basic preventive needs. Often restricted in certain states.
Sweet spot: Worth the investment for serious lawn enthusiasts, large areas, or persistently problematic disease situations where standard products have failed.
Pro Tips for Success
1. Before You Buy
Identify your specific disease problems first – take photos of affected areas and research which diseases commonly affect St Augustine in your region. This ensures you choose products with proven activity against your actual problems.
2. First Application
Apply during cooler parts of the day and ensure adequate soil moisture for systemic products. Mark your application areas and dates to track effectiveness and plan follow-up treatments.
3. Ongoing Maintenance
Monitor weather conditions and grass stress levels to time applications optimally. Preventive applications before stress periods are more effective than reactive treatments after disease appears.
4. When to Upgrade
If you're repeatedly treating the same areas or seeing disease return quickly after treatment, step up to a more powerful systemic product with longer residual activity.
Our Top Picks
Based on analysis of 2,500+ verified customer reviews
Atticus Gravex 20 EW
Professional-grade chemistry with systemic action provides the most comprehensive disease control. The concentrate format delivers exceptional value per application while matching golf course-quality results.
Scotts DiseaseEx
Simple spreader application eliminates mixing complexity while delivering reliable azoxystrobin-based control against major St Augustine diseases.
Spectracide Immunox
Addresses both disease and insect problems in one convenient application, providing exceptional value for homeowners facing multiple lawn stressors simultaneously.
Disclosure & Transparency
This article contains affiliate links to Amazon.com. As an Amazon Associate, I earn from qualifying purchases at no additional cost to you. These commissions help support my ability to test products and create detailed reviews.
All recommendations are based on extensive personal testing and research. I only recommend products I genuinely believe in and would use myself. Prices and availability are subject to change.