Quinclorac is a selective systemic herbicide best known for controlling crabgrass in turf and barnyardgrass in rice, although its exact weed spectrum depends on the registered product, application timing and use site.
It belongs to the quinoline-carboxylic acid family and is classified as a synthetic auxin herbicide. Quinclorac can be absorbed through foliage and roots, after which susceptible weeds develop abnormal growth and eventually decline.
However, many practical questions about quinclorac cannot be answered with one universal rule. Turf tolerance, application rate, surfactant requirements, reseeding intervals and target weeds can vary between formulations and labels.
This FAQ explains the most important quinclorac questions while separating general herbicide principles from product-specific instructions.
For a commercial formulation example, see Quinclorac 250 g/L SC from POMAIS.
Quinclorac Basics
What Is Quinclorac?
Quinclorac is a selective herbicide used in several grass-weed management programs.
Two of its most important use areas are:
- post-emergence crabgrass management in labeled turfgrass;
- barnyardgrass and other susceptible weeds in registered rice programs.
Quinclorac is available in different commercial formulations and concentrations depending on the market.
A formulation such as Quinclorac 25% SC uses a suspension concentrate system, while other registered products may use different formulation types.
The formulation does not change the identity of the active ingredient, but it can affect handling, mixing instructions, application rate and other product-specific requirements.
How Does Quinclorac Work?
Quinclorac is a synthetic auxin herbicide.
It is generally classified in Herbicide Resistance Action Committee / WSSA Group 4, together with other auxin-mimic herbicides.
After susceptible weeds absorb quinclorac, normal plant growth regulation is disrupted. Sensitive plants may show abnormal growth, chlorosis, tissue damage and eventual death.
Quinclorac is systemic, meaning the herbicide can move within susceptible plants after uptake.
Its activity should not be confused with a contact herbicide that only damages the tissue directly hit by spray droplets.
Is Quinclorac a Selective Herbicide?
Yes. Quinclorac is considered selective when used on labeled crops or turf species according to the approved rate and application instructions.
“Selective,” however, does not mean safe on every grass.
Tolerance varies among:
- turfgrass species;
- cultivars;
- growth stages;
- application rates;
- environmental conditions.
Always confirm that the target turf or crop appears on the specific product label before application.
Is Quinclorac Pre-Emergence or Post-Emergence?
Quinclorac is best known for post-emergence weed control, particularly against crabgrass in turf.
However, describing quinclorac as exclusively post-emergence would be too broad.
Some registered rice programs can use quinclorac where soil activity contributes to weed control, and application timing varies by crop and product.
For turf users, the safest general rule is:
Treat quinclorac as a product whose timing must be determined from the specific label and target weed growth stage.
Do not assume one application timing applies to every quinclorac formulation.
What Weeds Does Quinclorac Control?
Quinclorac is particularly important where certain annual grass weeds are the main target.
Its weed spectrum is not universal, so the label should always determine whether a particular species is controlled.
Does Quinclorac Kill Crabgrass?
Yes. Crabgrass is one of the best-known targets of quinclorac in turfgrass programs.
Quinclorac is widely used against species such as large crabgrass and smooth crabgrass where the product is registered.
Performance depends on factors including:
- crabgrass growth stage;
- application rate;
- active weed growth;
- environmental conditions;
- spray coverage;
- adjuvant requirements;
- herbicide susceptibility.
Very mature, stressed or resistant crabgrass populations may respond less consistently than actively growing susceptible weeds.
For a more application-focused discussion, see the POMAIS guide to quinclorac for lawn crabgrass control.
Does Quinclorac Control Barnyardgrass?
Yes. Barnyardgrass, including susceptible Echinochloa species, is another major quinclorac target.
This is particularly important in rice production, where barnyardgrass can compete strongly with the crop for light, nutrients and growing space.
Quinclorac use in rice should be based on:
- locally registered crops;
- weed growth stage;
- rice production system;
- water-management conditions;
- application timing;
- resistance history.
Repeated reliance on quinclorac alone can increase selection pressure, so resistance management should be part of long-term barnyardgrass programs.
Does Quinclorac Control Foxtail?
Some quinclorac labels include activity against certain foxtail species, but control can be less consistent than its well-known activity against crabgrass or barnyardgrass.
Do not generalize “foxtail” as a single weed.
Different species and growth stages may respond differently.
Where foxtail is the primary target, confirm the exact species and product label before selecting quinclorac.
Does Quinclorac Control Broadleaf Weeds?
Quinclorac can suppress or control some broadleaf weeds, depending on the product and use site.
However, it should not be treated as a universal broadleaf herbicide.
If the weed problem consists mainly of broadleaf species, another labeled herbicide or combination program may provide a more appropriate spectrum.
The key is to match the herbicide to the actual weed community rather than choose quinclorac simply because it is selective.
What Weeds Does Quinclorac Not Control Well?
Quinclorac does not reliably control every grassy or broadleaf weed.
Poor performance may occur when:
- the weed is naturally outside the herbicide spectrum;
- the plant is too mature;
- the weed is under environmental stress;
- application timing is incorrect;
- the local population has reduced sensitivity;
- coverage or adjuvant requirements are not met.
This is why weed identification should come before herbicide selection.
A grass weed that resembles crabgrass may require a completely different active ingredient.
Is Quinclorac Safe for Turfgrass?
Quinclorac can be used selectively on several labeled turfgrass species, but turf safety is species- and product-dependent.
A herbicide being safe on one established turf species does not guarantee equivalent tolerance on another.
Application rate, turf stress, temperature and growth stage can also influence injury risk.
Can Quinclorac Be Used on Bermudagrass?
Some quinclorac products are labeled for use on established bermudagrass.
However, tolerance and use restrictions vary by formulation and label.
Do not apply quinclorac to bermudagrass solely because another quinclorac product is approved for that turf.
Confirm:
- turf species;
- establishment status;
- application rate;
- temperature restrictions;
- overseeding instructions.
Can Quinclorac Be Used on Fescue?
Certain quinclorac products are registered for use on labeled fescue turf, particularly where crabgrass control is required.
Again, the product label is the deciding document.
Differences between tall fescue, fine fescues and other turf types mean that “fescue” should not be treated as one universal tolerance category.
Can Quinclorac Be Used on Newly Seeded Turf?
Possibly, but this is highly product-specific.
Some quinclorac turf labels provide instructions for use around seeding or new turf establishment, while others impose restrictions.
Do not rely on a general statement such as “wait one week after quinclorac.”
Instead, check the exact label for:
- seeding interval;
- overseeding restrictions;
- turf species;
- application rate;
- number of applications.
This is especially important where turf establishment and weed control occur at the same time.
Quinclorac Application and Timing
How Long Does Quinclorac Take to Work?
Quinclorac is not normally an instant burndown herbicide.
Visible symptoms can develop after treatment, while complete decline may take longer.
Control speed depends on:
- weed species;
- growth stage;
- temperature;
- plant stress;
- application rate;
- formulation;
- adjuvant system.
The absence of immediate browning does not necessarily mean the treatment has failed.
Because quinclorac acts systemically, weed response should be assessed over the period described on the product label rather than judged immediately after spraying.
When Is the Best Time to Apply Quinclorac?
For post-emergence use, quinclorac generally performs best when the target weed is actively growing and within a susceptible growth stage.
Timing can strongly influence crabgrass control.
Young weeds may respond differently from mature, multi-tiller plants, while drought, heat stress or other unfavorable growing conditions may reduce herbicide uptake and activity.
The most appropriate timing should therefore be determined by:
- target weed;
- growth stage;
- use site;
- product label;
- environmental conditions.
Does Quinclorac Need a Surfactant?
Some quinclorac products recommend or require an adjuvant, while others are formulated or labeled differently.
Therefore:
Do not automatically add a surfactant to every quinclorac application.
The correct adjuvant may depend on:
- formulation;
- target weed;
- crop or turf;
- spray carrier;
- product label.
Using an inappropriate surfactant can increase crop or turf injury or change spray performance.
How Much Quinclorac Should I Use?
There is no universal quinclorac dose.
Application rate depends on the concentration and formulation of the commercial product.
For example:
250 g/L SC
25% SC
different dry formulations
cannot be converted into one generic “ounces per acre” or “milliliters per gallon” recommendation without reading the label.
The rate also depends on:
- weed species;
- weed growth stage;
- turf or crop;
- application method;
- local registration.
Use the rate stated on the specific registered product.
How Soon Can You Seed After Applying Quinclorac?
There is no universal reseeding interval for every quinclorac herbicide.
Some turf labels permit applications close to seeding under specific conditions, while others impose waiting periods.
Always follow the exact instructions for:
- reseeding;
- overseeding;
- sod installation;
- crop rotation.
Avoid copying a waiting period from one quinclorac product onto another.
Can Weeds Become Resistant to Quinclorac?
Yes.
Repeated use of the same herbicide mode of action can select individuals that are less sensitive to the treatment.
Quinclorac resistance has been documented in weed populations, including important grass weeds.
This does not mean quinclorac is ineffective in general. It means repeated dependence on one active ingredient can reduce long-term sustainability.
Resistance-management practices can include:
- rotating herbicide modes of action;
- combining chemical and nonchemical weed control;
- controlling survivors before seed production;
- monitoring declining performance;
- identifying the weed correctly;
- avoiding repeated unnecessary applications.
If a weed population survives an application that previously provided good control, do not immediately increase the dose beyond the label.
First investigate application conditions, growth stage, coverage and possible resistance.
For programs combining different herbicide timings, BigPesticides also discusses the mixing of prodiamine and quinclorac as part of pre- and post-emergence weed-management strategies.
Quinclorac vs Other Herbicides
Quinclorac is often compared with other selective herbicides, but “better” depends on the target weed and site.
Quinclorac vs Mesotrione: Which Is Better?
Quinclorac and mesotrione have different modes of action and different strengths.
Quinclorac is particularly well known for post-emergence crabgrass control.
Mesotrione has a broader role in some cool-season turf programs and is used against various grassy and broadleaf weeds, depending on the label.
The better choice therefore depends on:
- target weeds;
- turf species;
- weed stage;
- seeding situation;
- resistance-management needs.
BigPesticides already provides a dedicated comparison in Quinclorac vs Tenacity (Mesotrione): Which Herbicide Is Better for Grass Weed Control?.
Quinclorac vs 2,4-D: What Is the Difference?
Quinclorac and 2,4-D are both associated with synthetic auxin herbicide activity, but their practical weed-control roles are different.
Quinclorac is especially important for certain grass weeds, including crabgrass and barnyardgrass.
2,4-D is much more strongly associated with broadleaf weed control.
Therefore, the important comparison is not simply their hormone-related mode of action.
The real difference for users is:
- weed spectrum;
- crop or turf selectivity;
- application program;
- formulation;
- registered use site.
A lawn dominated by crabgrass presents a different herbicide-selection problem from one dominated by dandelion or other broadleaf weeds.
Frequently Asked Questions
Is Quinclorac Systemic or Contact?
Quinclorac is systemic. It is absorbed by susceptible plants and moves within plant tissues after uptake. It should not be treated as a fast contact-burn herbicide.
Is Quinclorac the Same as 2,4-D?
No. They are different active ingredients and have different chemical identities and weed-control spectra, even though both are associated with synthetic auxin herbicide action.
Can Quinclorac Be Tank-Mixed With Other Herbicides?
Some registered quinclorac products permit specific tank mixtures, but compatibility and crop safety depend on the products involved. Check both labels before tank mixing and follow any compatibility or jar-test instructions.
Does Rain Affect Quinclorac?
Rainfall shortly after spraying can affect foliar herbicide performance if the treatment has not had sufficient time to dry or be absorbed. The required rain-free interval depends on the specific commercial product.
Can Quinclorac Damage Grass?
Yes, if it is used on an intolerant species, at an incorrect rate or under unsuitable conditions. Turf safety must be confirmed from the label rather than assumed from the active ingredient alone.
What Is the Most Important Thing to Know About Quinclorac?
Quinclorac is a valuable selective herbicide, particularly for crabgrass in turf and barnyardgrass in rice, but successful use depends on more than choosing the correct active ingredient.
Weed identification, growth stage, formulation, turf or crop tolerance, application timing and resistance history all influence the result.
For technical users, quinclorac should therefore be viewed as one herbicide tool within a broader weed-management program rather than a universal solution for every grass weed.
For importers, distributors and crop-protection brands looking for commercial quinclorac products, POMAIS supplies Quinclorac 250 g/L SC and other selective herbicide formulations for registered market programs, formulation customization and private-label supply.
Post time: Jul-16-2024
