It depends. Atrazine is widely discussed for use in St. Augustinegrass turf in some markets, but the real decision is governed by cultivar sensitivity (especially Floratam), turf stress and temperature, and label-driven environmental constraints (runoff and groundwater protection). Always follow the product label and local regulations.
This evergreen knowledge article is written for turf professionals, distributors, and procurement teams who need decision-grade clarity: what atrazine is, how it works, what it tends to be used for in St. Augustine lawns, why injury happens, and what to verify before sourcing or importing atrazine for turf markets.
What is atrazine in the turf context?
Atrazine is a triazine herbicide most commonly classified as a photosystem II (PSII) inhibitor (Group 5 in HRAC/WSSA systems). In practical turf terms, it is a plant-active chemistry used to manage certain weed pressures where the label allows, while requiring careful stewardship because environmental movement (especially toward water) is a central compliance concern.
Why this matters for St. Augustinegrass
St. Augustinegrass is a warm-season turfgrass with multiple cultivars in the market. “St. Augustinegrass” on a label does not automatically mean “every cultivar under every condition.” University guidance repeatedly highlights cultivar-specific tolerance and temperature/stress sensitivity as the main failure mode in lawn programs.
Can you use atrazine on St. Augustinegrass?
Sometimes—if the product label explicitly supports your use pattern and your cultivar/conditions are within tolerance. In lawn markets, atrazine is often positioned for broadleaf weed management and seasonal weed pressure, but the decision should be made as a risk-managed fit, not a default choice.
The “decision boundary” you should treat as non-negotiable
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Label scope: the label is the operating system—use sites, turf species, limitations, and environmental hazard statements define what is permitted.
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Cultivar tolerance: Floratam in particular is repeatedly flagged as sensitive.
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Stress/temperature window: multiple UF/IFAS resources note injury risk increases in hotter conditions for St. Augustine programs.
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Environmental constraints: groundwater/runoff language can be explicit on atrazine labels and can restrict suitability in certain soils and sites.
Do St. Augustine cultivars differ in atrazine tolerance?
Yes. This is the single most important reason atrazine programs “work fine” for one lawn and cause injury in another.
Floratam: consistently flagged as high-risk
UF/IFAS guidance states Floratam is not tolerant of herbicides containing atrazine when applied at temperatures above 85°F. Texas A&M turf guidance also warns that Floratam is not tolerant to herbicides containing atrazine and will be injured.
Why procurement teams should care
Cultivar sensitivity is not a minor technicality—it changes:
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Customer complaint rate and brand risk in retail/pro channels
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Label, training, and stewardship burden for distributors
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After-sales support cost (damage claims, reputation, re-treatment disputes)
If you sell into markets where Floratam is common, your go-to-market plan must treat “cultivar sensitivity” as a front-page disclosure, not fine print.
How does atrazine work?
Atrazine interferes with photosynthesis by inhibiting photosystem II, which disrupts energy production in susceptible plants. Group 5/PSII inhibitor injury is commonly associated with chlorosis (yellowing) that can progress to necrosis (browning/tissue death) depending on the plant and exposure scenario.
Selectivity is conditional, not absolute
Selectivity in turf is best understood as a margin: when turf is healthy and conditions are within tolerance, the margin is wider; when turf is stressed or a cultivar is sensitive, the margin narrows and visible injury becomes more likely. UF/IFAS lawn guidance directly ties higher-temperature conditions to atrazine intolerance in Floratam, which is a practical example of that margin shrinking.
What does atrazine control in St. Augustine turf?
Atrazine is typically discussed in lawn programs for broadleaf weed control and seasonal broadleaf pressure where labels allow, with some communications framing it as a post-emergence tool for certain broadleaf weeds in St. Augustine lawns.
A buyer-safe way to frame “weed spectrum”
For a commercial page that must remain compliant and non-instructional, you should frame weed control like this:
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Primary value: broadleaf weed pressure in permitted lawn/turf sites
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Limitations: spectrum is label-defined, and performance is context-dependent (weed growth stage, turf density, weather, and site conditions)
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Program reality: atrazine is not a cure for thin turf; weeds exploit weak turf, so long-term control is tied to turf vigor and site management
(If you want, I can also produce a “label-style weed category list” that avoids doses/steps and stays within decision-grade language.)
Why does atrazine sometimes injure St. Augustinegrass?
Most lawn injury cases trace back to one of four drivers:
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Cultivar mismatch (Floratam risk)
UF/IFAS and Texas A&M guidance both explicitly flag Floratam sensitivity. -
Heat/stress narrows selectivity
UF/IFAS materials warn about atrazine intolerance in Floratam above 85°F, and IFAS extension communications note that atrazine may damage St. Augustine and other lawns at higher temperature ranges. -
Site conditions amplify exposure
Compacted soils, poor drainage, and heavy runoff potential increase environmental movement risk and can also correlate with stressed turf performance—two problems that often stack together in the real world. -
Diagnosis confusion
Yellowing/browning patches can be misattributed; without context (cultivar, recent inputs, weather), herbicide injury and other turf stressors may look similar at a distance. (This is where professional diagnostics and documentation reduce disputes.)
Compliance & environmental constraints
Atrazine is a compliance-led active ingredient. In the U.S., atrazine labels can include explicit groundwater language such as: atrazine can leach, has been found in groundwater, and users are advised not to apply on sand/loamy sand soils with shallow water tables due to higher contamination risk.
What this means for turf buyers and distributors
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Your marketability is partially environmental: certain geographies and soil profiles increase stewardship burden.
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Your documentation pack matters: customers will ask for SDS/COA and for clarity on environmental hazard statements and permitted sites.
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Your label strategy affects sales velocity: a “turf-ready” label that is clear on permitted sites and limitations reduces friction in distributor onboarding.
Bees & other non-target considerations
Atrazine is an herbicide, not an insecticide. NPIC’s fact sheet states atrazine is practically non-toxic to honeybees through short-term contact or ingestion, and EPA’s atrazine interim decision notes available acute bee data indicate atrazine is practically non-toxic on an acute exposure basis (while also acknowledging uncertainty due to incomplete suites of terrestrial invertebrate studies).
The practical pollinator conversation is often indirect
Even when acute toxicity is low, stewardship discussions can still involve:
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Habitat/forage shifts if flowering weeds are removed
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Off-site movement affecting non-target vegetation near lawns and landscaped areas
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Stakeholder perception risk (public sensitivity is high even for herbicides)
In high-visibility markets, buyers often prefer a supplier that can provide a clear, evidence-based pollinator positioning statement aligned with NPIC/EPA language—without making overconfident claims.
Regulatory lens: why “legal” is market-specific
Atrazine’s regulatory status is not uniform across jurisdictions. In the EU, a 2004 Commission Decision addressed the non-inclusion of atrazine under the then-applicable framework, referencing concerns around groundwater contamination thresholds and monitoring evidence.
Procurement implication: if you import or private-label across regions, you need a jurisdiction-by-jurisdiction clearance process (registration status, permitted uses, label language, and documentation requirements), not a one-size-fits-all assumption.
Quick decision table: Is atrazine a fit for your St. Augustine program?
FAQ
Is atrazine safe for St. Augustinegrass?
It can be, but only if the label supports your use pattern and your cultivar and conditions are within tolerance. Floratam is explicitly flagged as not tolerant of atrazine-containing herbicides above 85°F in UF/IFAS guidance.
Why does atrazine burn or yellow St. Augustine lawns?
Most cases trace to cultivar sensitivity (especially Floratam), turf stress/heat conditions, and site factors that reduce the margin of selectivity. UF/IFAS and IFAS extension communications directly tie hotter conditions to higher injury risk in St. Augustine lawns.
Does atrazine contaminate groundwater?
Atrazine labels can explicitly warn that atrazine can leach, has been found in groundwater, and advise against use on certain sandy soils with shallow water tables due to contamination risk.
Is atrazine toxic to bees?
Public summaries indicate low acute toxicity to honeybees. NPIC describes atrazine as practically non-toxic to honeybees via short-term contact or ingestion, and EPA’s interim decision similarly describes available acute data as practically non-toxic, while noting data gaps for a complete invertebrate assessment.
Is atrazine banned worldwide?
No. Regulatory status varies by country. The EU issued a 2004 decision addressing non-inclusion linked to groundwater contamination concerns, illustrating how market access can differ sharply across jurisdictions.
Next steps for evaluation
If you are sourcing atrazine for turf and lawn markets, start with a label-ready documentation pack: SDS/TDS, batch COA template, confirmed permitted use sites for St. Augustinegrass, and a short compliance summary that aligns environmental hazard language with your target geography.
Post time: Feb-10-2026
