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Cloransulam-methyl didn’t just pop up overnight. Its roots grow from the constant pressure farmers felt as weeds grew stubborn against traditional controls. Back in the early 1990s, big chemical players poured research dollars into discovering new herbicides, motivated by fields overtaken by pigweed and other tough broadleaf invaders. Somebody in the lab finally cracked the code with cloransulam-methyl, a molecule designed to shut down weed growth without nuking the crop itself. Field tests spread through soybean-growing states. Results made a quick statement: this compound showed real promise. The EPA signed off on its use toward the late ‘90s, and farmers across the Midwest added it to their weed-control toolkit not because they wanted something new, but because they needed something reliable.
Farmers know cloransulam-methyl by names like FirstRate and Authority First. In the jug, it’s a granular or sometimes a powered concentrate. After mixing with water, applicators ride fields spraying it across pre-emergent or early post-emergent stages of soybeans. No one likes dealing with harsh smells or tough residues, so product makers worked to make it as clean to handle as possible. People count on it to target broadleaf weeds, especially those resistant to other ALS inhibitors. Folks in ag retail look for its registration as a Group 2 herbicide, clear proof it works differently from the standard glyphosate playbook.
Look at the actual substance: light beige powder, not much smell, barely noticeable to the nose. Cloransulam-methyl doesn’t dissolve well in plain water, which is why it’s usually formulated with surfactants and solvents to stick to weeds. It melts at about 163°C, way beyond typical field temperatures. Chemically, it’s known for stability under storage but can break down when mixed too long with strong acids or bases. It challenges weed enzymes by slipping into the plant’s cellular machinery and blocking acetolactate synthase, shutting off critical amino acid production and starving the weed from within.
Manufacturers stamp every jug of cloransulam-methyl with detailed guidance because spray drift and overlapping rates bring legal headaches. Most labels set use rates between 0.3 to 0.6 ounces per acre, flagging timing so the crop escapes injury and weeds catch the full dose. Spray volumes and droplet sizes aren’t just suggestions; they make or break success out in the field. Labels also urge users to tank-mix with other tools to fight resistance. Each package reminds the user about rainfastness, re-entry intervals, and buffer requirements, especially near waterways and sensitive habitats. Any lapse can lead to crop stunting or non-target injuries—farmers know to pay close attention.
Making cloransulam-methyl starts with some heavy-duty organic chemistry, combining a triazolopyrimidine ring with chlorinated and methylated side chains. Research chemists developed stepwise syntheses, usually involving protected starting materials, controlled chlorination, and methylation under anhydrous conditions. The last production step forms an ester bond, which brings environmental degradability within reach since microbes eventually chop up the compound after it does its work. Manufacturing plants feature reaction vessels built to handle corrosive reagents and high purity needs. Finished product batches wind up rigorously tested for residual solvents, water content, and particle size, which all shape its storage characteristics and mixability at the co-op.
In the environment, sunlight and soil microbes chip away at cloransulam-methyl through hydrolysis and demethylation. Chemists in the lab tinker with its backbone, sometimes swapping out substituents to tweak environmental persistence or touch up selectivity. Companies tested analogs early on, but most didn’t deliver the right blend of crop safety and field control. The methyl ester boost helps with uptake and efficacy on-field but creates a balance since it also affects degradation times. In tank mixes, it sometimes antagonizes or synergizes with other actives, prompting research into best-fit combinations and timing for rotation programs.
You won’t just hear cloransulam-methyl from chemists, as growers recognize it as FirstRate or Authority First for soybeans. Regulatory documents sometimes list it as methyl 2-chloro-N-(2,6-diethoxypyrimidin-4-yl)-6-(trifluoromethyl)pyrimidine-4-carboxamide, but nobody outside a laboratory uses that mouthful. A few off-patent producers call it by generic names, though most stick to the main trademarks recognized in ag supply stores. In Brazil and Argentina, a couple of alternate brands package it alongside local language labeling.
Field crews know you can’t let safety slip. With cloransulam-methyl, gloves and goggles serve as standard kit, especially when mixing and loading concentrates. Folks rely on closed transfer systems and proper tank-cleanout procedures. The EPA classifies it as “slightly hazardous” for acute oral and dermal toxicity—a relief compared to legacy herbicides, but caution remains. Re-entry intervals on the label typically allow workers back in the field after twenty-four hours, assuming minimal residual hazard. Emergency protocols cover eye exposure and accidental spills, and local extension offices provide annual safety training so no one guesses when handling these products. No operator trusts shortcuts: plenty of folks have stories about drift and improper disposal harming the next field over.
Soybean growers make up the largest group using cloransulam-methyl, especially across the U.S. corn belt. Some peanut growers in southern states rely on it for tough weed patches, while occasional international markets (like in South America) use it for both soybeans and select legumes. The active ingredient faces weed species switching with the times; ragweeds and marestail joined the list as resistance to older modes of action spread. No orchard or vineyard grower puts it in the tank, since crops sensitive to ALS inhibitors can burn and suffer with minor drift. Most ag retailers advise it for pre- and early post-emerge use, giving most bang-for-the-buck before row closure. County extension agents spread the word on best-fit rates and stewardship, aiming to keep the tool effective down the road by rotating with other chemistries.
University weed science programs and private ag chemistry labs never stop testing cloransulam-methyl’s performance. Over the years, field researchers documented shifts in weed response, finding some biotypes slowly growing tolerant. That data pushed companies to sponsor trials combining cloransulam-methyl with other actives to slow resistance, optimize timing, and protect future tools. Recent studies examine its breakdown products in soil, watching where residues accumulate and whether they impact rotation crops or water tables. Labs in Asia and South America pursue new methylated and chlorinated derivatives, chasing after variants with lower dose requirements or extended residual action. Some researchers work with remote sensing and modeling to fine-tune application recommendations and minimize overlap.
Toxicologists checked both acute and chronic effects. Most reported low mammalian toxicity, backed by animal studies pointing to rapid breakdown after ingestion and little buildup in tissue. Birds and bees faced low risk at normal exposure levels. Researchers focused more on aquatic impacts, as run-off into streams and ditches sometimes affected sensitive species, especially algae and invertebrates. That drove product stewardship toward buffer strips around water and re-entry delay reminders for workers with a history of skin sensitivities. Chronic feeding trials on rodents checked for reproductive and developmental risks, with results showing safety margins well beyond normal dietary intake. State agencies pay attention to groundwater monitoring in areas with heavy use, measuring for any breakdown products that might sneak through the soil.
Cloransulam-methyl faces an uphill fight against resistance. Weeds adapt, and the ALS-inhibitor group has felt real pressure as old standbys like Pursuit and Classic lost ground to resistant Palmer amaranth and waterhemp. Farmers asking for new modes of action or premixes see industry efforts to blend cloransulam-methyl with complementary actives as a partial fix, though everyone in ag understands it’s only as good as the stewardship behind it. Advances in precision application—think drone sprayers and machine learning weed ID—hold promise for squeezing the most out of each ounce, stretching this tool’s life a bit longer. The regulatory scrutiny keeps tightening, too, forcing companies to keep environmental profiles and user safety high on the to-do list. Eventually, progress in biologicals or next-generation chemistries might shrink cloransulam-methyl’s share of the herbicide market, but today, growers depend on its targeted power to stay ahead of some the most stubborn weeds threatening yields each season.
Out in the soybean fields, cloransulam-methyl works as a pre-emergence and post-emergence herbicide. It knocks out broadleaf weeds that threaten young soybean plants. Allergic to marketing jargon, farmers simply call it a "problem solver" for pigweed, velvetleaf, lambsquarters, and smartweed. Weeds keep adapting, getting tougher every season. One whiff of hot weather and rain, and you can practically see pigweed sprout overnight. Without this herbicide, yields take a beating, profits fall, and a farmer’s hard work washes away with the next thunderstorm.
Spraying cloransulam-methyl before the soybeans break ground gives seedlings a head start. If the weeds come up later or sneak through the initial treatments, another application mops up the stragglers. The science behind it involves blocking ALS (acetolactate synthase) enzymes in the weeds. Take out that enzyme; growth stops, and the intruder goes limp. The soybean plants, which don’t carry the same weak spot, grow on. No need for gardeners to worry; this isn’t something you'd sprinkle in a flower bed. Its role fits a precise piece of the row-crop puzzle.
I’ve seen neighbors wrestle with resistant pigweed that laughs at older herbicides. Turning over fields or running cultivators cost fuel and time. Some folks joke that after weeks of weeding, you start rooting for the crop to survive rather than for the yield itself. Cloransulam-methyl took some of the pressure off. It gave us an option when other treatments didn’t work. That alone explains why farmers in the Midwest, and further south, kept it in the spray shed.
No one gets to rest easy. Rotation keeps plants guessing, but resistance has crept up. ALS inhibitors like cloransulam-methyl face pushback as weeds shift and build tolerance. According to university tests, pigweed in several states now resist more than one chemical group. Experts urge mixing modes of action in herbicide programs, not putting loyalty in just one product. We only get to use these tools if we use them wisely.
Farmers watch for weather, drift, and water runoff. Some chemicals travel downstream, hurting fish and plants. Fortunately, cloransulam-methyl breaks down fairly quickly in soil. University research put its half-life around two weeks in warm, moist dirt. It doesn’t build up, but that doesn’t mean it gets a free pass. Spraying banners along ditches or windy fencerows leads to trouble. Some states require buffer zones to keep the herbicide from waterways.
The lesson goes beyond a single herbicide. Rotating crops, scouting fields, mixing up spray patterns, and picking products for local weeds all matter. Every field needs a plan made from experience, talking to crop consultants, and checking university data. Relying on one answer lets resistance sneak back in. New research and smart stewardship can keep these fields productive and healthy.
Cloransulam-methyl turns up in conversations about weed control on farms, especially in soybean fields. If you haven’t heard the name before, picture those high summer days out in the field, pulling pigweed that laughs at your old mower. That’s where this chemical comes into play, promising relief for farmers who want clean rows of beans. The real question a lot of folks are asking: does it keep crops and the people who eat them safe?
Every year weeds threaten yields and hit a grower’s bottom line. Many herbicides go after everything green, but broadleaf weeds can outsmart the classics. Cloransulam-methyl targets these tough invaders and clears space for soybeans to stretch out and thrive. The United States Environmental Protection Agency (EPA) says that, when used as directed, it works without harming the beans. It breaks down in soil and doesn’t stick around longer than it should, which matters if folks plant food crops year after year.
Digging into the research, large studies show cloransulam-methyl doesn’t build up in beans themselves. The U.S. EPA and agencies in Canada and Europe reviewed animal and environmental studies before approval. Field trials help show residue remains below amounts considered risky for human health. Environmental impact checks reveal low toxicity for birds, mammals, and insects like bees, when farms follow labeled instructions.
This matters to buyers at the grocery store. No one wants hidden toxins in their salad. Regulators ran the numbers on how much a person might take in over a lifetime through food—even if that food comes straight from a big soybean field. So far, the math lines up with health standards, which brings some peace of mind.
Even with official approvals, some voices remain skeptical. Years spent around farming families and in small-town co-ops taught me that trust doesn’t come easily. Neighbors hear about chemical drift, water runoff, or questions from buyers in countries with stricter rules. Newspaper stories about resistance also pop up: weeds can adapt, which could corner farmers into stronger or riskier chemicals down the road.
Some farmers I know stick to rotation, cover crops, and hand-pulling when they can, not because they don’t trust science but because they remember the times products once labeled as safe later turned out to cause harm. As anyone who’s seen “the back forty” turn yellow from the wrong chemical knows, mistakes last in the ground and linger in the community.
Farmers who rely on cloransulam-methyl can take a good, hard look at integrated weed management. Mixing chemical control with non-chemical options, like rotating crops and planting cover crops, cuts down how much herbicide ends up in the dirt. Regular soil tests track breakdown, making it easier to know if things are on the right track or if something’s starting to build up. Universities offer farm outreach, helping folks sort safe practices from risky shortcuts.
Ag companies and regulators should listen more closely to farmworkers and rural neighbors. Communities near fields want clear updates on research and safety. Labels come with long legal wording, so practical safety training helps—real advice for mixing, spraying, and cleaning up. Giving the public access to up-to-date field study results, not just summaries, lets everyone judge the risks for themselves.
Safe farming often means blending reliable science with lessons learned right on the ground. Cloransulam-methyl brings real benefits, but ongoing attention, open reporting, and a few healthy doubts from the people who live with these chemicals daily keep the balance in check.
Few things test the patience of a farmer like weeds stealing nutrients, sunlight, and water from crops. Cloransulam-methyl rolled out in the late 1990s to help soybean growers tackle tough broadleaf weeds in their fields. This active ingredient works by blocking a critical enzyme—acetolactate synthase (ALS)—inside the plant. Without it, weeds can’t produce essential amino acids. Growth stops. Death isn’t immediate, but it’s predictable.
Weed management takes up time, fuel, and money. Growing up, I watched neighbors struggle with morningglories and pigweed overtaking their soybeans and ruining returns. Hand-pulling never kept up. Cloransulam-methyl brought a targeted approach. It knocks back more than 50 types of broadleaf weeds, which saves more of the crop’s nutrients for feeding families, not freeloading pests.
Spraying smarter, not harder, caught on. Unlike older herbicides, cloransulam-methyl works at low application rates—less than one ounce per acre. That’s a big leap toward less chemical load on the environment and smaller hit to a grower’s wallet. Waterways end up cleaner, and beneficial insects stick around longer in the fields.
A molecule’s magic often happens at the cellular level. After application, the weed absorbs the herbicide through its leaves and roots. ALS inhibitors like cloransulam-methyl block protein formation, halting photosynthesis and growth. Soybeans, on the other hand, survive exposure because scientists bred built-in resistance into some varieties. That means less crop injury and more consistent yields.
Field trials from university extension offices back up these claims. Reports in Iowa and Illinois show that cloransulam-methyl cuts common ragweed populations by over 95 percent with a single application. Not every field looks the same, though. Humid conditions, heavy clay soils, or drought can all make or break how well the treatment sticks and does its job.
Every good thing faces challenges—none more serious than herbicide resistance. Overusing a single chemistry, like cloransulam-methyl, pushes weeds to adapt. Waterhemp and Palmer amaranth are already catching up. Without change, more farmers might find their crops choked once again.
One obvious fix starts with rotation—not just crops, but herbicide types. Mixing ALS inhibitors with herbicides that work differently slows weed resistance. No magic bullet exists; it’s all about building a strong, flexible defense. Investing in on-farm research or working with local agronomists pays off in the long run.
Farmers also look at integrated tactics: cover crops, no-till, precision spraying, and timing applications better. These approaches mean fewer weeds ever get established. One neighbor told me he spent less time fighting weeds last year because he mixed mowing and alternating herbicides, not just relying on the same product year after year.
Modern farmers care about producing safe, affordable food and protecting their fields for future generations. Cloransulam-methyl brought in a more surgical approach to weed control that saves resources and minimizes runoff. It’s not a cure-all, but it gave growers a break from the endless weed wars. Staying ahead means combining technology, biology, and plain old observation—so the story of this herbicide keeps evolving with every changing season.
Farmers have faced weeds for as long as seeds have gone into the soil. Years spent seeing soybeans overrun with pigweed or ragweed taught many of us how easily a whole season’s work can get choked. Cloransulam-methyl showed up in the late 1990s and kept changing how growers took control of broadleaf weeds. Though most folks will call it a soybean herbicide, there’s a larger story about what gets planted and what can be protected.
Soybeans make up the main field for cloransulam-methyl. Its selective action gives soybeans an edge against nightmares like velvetleaf, waterhemp, lambsquarters, and marestail. Pre-emergence and post-emergence use let farmers pick the right timing for weed flushes. Decades of university field trials back up its effectiveness in the upper Midwest and along the Eastern soybean belt. Stories from agronomists and neighbors line up too: stunted pigweed patches and clean bean rows with regular rotation.
Peanuts sometimes benefit from cloransulam-methyl, but these uses never caught on broadly in the Southeast where peanuts are grown at scale. The mainstay remains with soy, since registration and label requirements get strict. The Environmental Protection Agency still lists peanuts in some technical documents, yet many co-ops and local suppliers keep this chemistry mainly for soybean fields due to market demands and risk tolerance.
Corn, sorghum, small grains, and alfalfa don’t share this option. Most grasses and cereal crops lack the tolerance, and the chemical’s selectivity works against only specific broadleaf weeds. Growers aiming to rotate from soybeans into these crops have to watch cloransulam-methyl’s soil persistence and plant-back intervals. Waiting periods can stretch a couple of months or longer before corn can be planted safely. This gap usually directs farmers toward other products during corn or small grain years.
Sticking mainly to soybeans limits resistance. Overusing a single herbicide family can wipe out options for entire regions. Herbicide resistance has become the number one headache for many. Pigweed populations in Delta states prove how quickly tough weeds outpace chemistry, and local Extension bulletins keep hammering away at rotating modes of action. South Dakota State and Purdue both documented reduced efficacy in fields exposed repeatedly to ALS inhibitors, the class including cloransulam-methyl. Spraying only the crops listed on the label protects this tool for the long haul and slows down resistance development.
Farmers and agronomists need more than one trick. Using cover crops, tillage, pre-mix herbicides, and integrating non-chemical options all help to keep weeds in check. Making sure cloransulam-methyl goes only on crops that support it—like row-crop soybeans—keeps it effective for years down the line. The answer isn’t always another chemical; most success comes from a balanced approach. Talking with Extension agents, reviewing local research, and sharing what works among neighbors all help build smarter herbicide plans that match both crop safety and weed control.
Years of working in agronomy have taught me that good weed control can protect a season’s yield. Farmers ask about Cloransulam-Methyl because it helps keep broadleaf weeds from robbing resources in their soybean fields. Most labels and guides recommend using between 0.02 and 0.04 pounds of active ingredient per acre. This narrow range comes from field research. It usually delivers season-long suppression of thistles, pigweed, bedstraw, marestail, morningglory, and more, all without hammering the crop.
Spraying above 0.04 pounds isn’t just a waste of cash. Studies from universities like Purdue and Iowa State show that going heavy with this herbicide doesn’t buy extra weed control. It can bring on crop stress or damage. More than a few experienced growers have seen leaves curl and yields fall, all because “a little extra can’t hurt.” So, sticking with the sweet spot—right there between 0.02 and 0.04 pounds—protects both pocketbooks and bushels.
I’ve seen that catching weeds young—not waiting until they’re waist-high—makes any program work better. Cloransulam-Methyl hits its stride sprayed before weeds get past four inches tall. Early burndown or pre-emergence tank mixes keep populations from exploding in the first place. If weeds already have the upper hand, rewind and rethink the approach. No single herbicide, not even Cloransulam-Methyl, saves the day for a field blanketed in pigweed that’s gone to seed.
Scouting every week shows when to act. Smart growers mix this chemistry with others, like glyphosate or metribuzin, because nobody wants resistance creeping in. Rotating actives stops weeds from learning new tricks and outsmarting science and seed in the long run.
Application rate isn’t a one-size-fits-all deal. Clay-heavy soils with lots of organic matter can tie up more herbicide, so label rates land on the high end. Lighter sand often needs the lower rate. Too much rain soon after spraying can wash expensive product off target. Drought can hold weeds in check, letting farmers dial down the rate. It pays to follow local Extension advice and check the label for specific resistant weed threats or sensitive crops nearby.
Cloransulam-Methyl offers effective control with a lighter touch than some older chemistries. Keeping the rate within bounds matters for more than just weeds. Experts warn about groundwater issues from overapplication. Sprayer calibration—checking nozzle size, pressure, and ground speed—keeps overuse in check and stops off-target drift into ditches or neighboring fields. Protective gear guards the skin and lungs of anyone mixing or spraying this herbicide. Safety guidelines have real payoffs, not just for compliance but for long-term health.
It’s tempting to count on any herbicide to solve all weed headaches, but decades of experience and updated research say otherwise. Programs that rely on more than one active ingredient, often including post-emergence rescue treatments and compete cover crops, continue to deliver better yields than any set-it-and-forget-it tank mix. Following the recommended rate leaves enough room in the budget to rotate products, scout more often, and commit to systems thinking. Weed control will never get easier, but sticking to proven rates and adapting with experience helps keep the battle in a farmer’s favor.
| Names | |
| Preferred IUPAC name | Methyl 2-[(4-chloro-6-methoxypyrimidin-2-yl)carbamoylsulfamoyl]benzoate |
| Other names |
FirstRate Cloransulam methyl N-(2-Carboethoxyphenyl)-5-ethoxy-7-fluoro(1,2,4)triazolo(1,5-c)pyrimidine-2-sulfonamide methyl ester |
| Pronunciation | /klɔːˈræn.sjʊ.læm ˈmɛθ.ɪl/ |
| Identifiers | |
| CAS Number | 146991-23-3 |
| Beilstein Reference | 163669 |
| ChEBI | CHEBI:91281 |
| ChEMBL | CHEMBL174276 |
| ChemSpider | 74991 |
| DrugBank | DB11450 |
| ECHA InfoCard | 03fc2b6e-7dd5-4adb-ab0b-3321261d6ae2 |
| EC Number | Cloransulam-Methyl" EC Number is "607-443-3 |
| Gmelin Reference | 837162 |
| KEGG | C14467 |
| MeSH | D016934 |
| PubChem CID | 86358 |
| RTECS number | DM8575000 |
| UNII | 1V2L87USG3 |
| UN number | “3077” |
| CompTox Dashboard (EPA) | DTXSID6022006 |
| Properties | |
| Chemical formula | C15H12ClN5O5S |
| Molar mass | 354.76 g/mol |
| Appearance | White solid |
| Odor | Odorless |
| Density | 1.48 g/cm³ |
| Solubility in water | 6.8 mg/L (25 °C) |
| log P | 1.9 |
| Vapor pressure | 1.60 x 10^-7 mmHg |
| Acidity (pKa) | pKa = 4.71 |
| Basicity (pKb) | pKb = 4.26 |
| Magnetic susceptibility (χ) | Diamagnetic |
| Dipole moment | 2.41 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 317.8 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -643.1 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | –6965 kJ·mol⁻¹ |
| Pharmacology | |
| ATC code | QH herbicides |
| Hazards | |
| Main hazards | May cause eye and skin irritation; harmful if swallowed or inhaled; avoid contact with eyes, skin, and clothing. |
| GHS labelling | GHS07, GHS09 |
| Pictograms | GHS07,GHS09 |
| Signal word | Caution |
| Hazard statements | H410: Very toxic to aquatic life with long lasting effects. |
| Precautionary statements | P261, P264, P270, P272, P273, P280, P301+P312, P330, P391, P501 |
| NFPA 704 (fire diamond) | 1-1-0- 가나다라마바사 |
| Flash point | > 97.2 °C |
| Lethal dose or concentration | LD₅₀ oral rat: >5000 mg/kg |
| LD50 (median dose) | LD50 (median dose): >5000 mg/kg |
| NIOSH | NA8480000 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 35 g ai/ha |
| Related compounds | |
| Related compounds |
Chlorsulfuron Ethamsulfuron-methyl Prosulfuron |
