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Metolachlor entered the global stage as a selective herbicide in the 1970s, changing the way farmers tackle weeds in corn, soybeans, cotton, and other crops. Companies started rolling it out to solve practical problems—namely, stubborn weeds that outcompete crops and drag down farm yields. Its discovery came from years of research into acetanilide compounds, many of which form the backbone of modern pre-emergent herbicides. The adoption of metolachlor kicked off an era where crop protection chemistry sharply improved, not just in effectiveness, but in reach. Farmers saw a noticeable boost in productivity and could rotate crops with more flexibility.
Metolachlor falls under the chloroacetanilide class. Folks use it before weeds begin emerging, targeting broadleaf and grassy invaders. It works by hitting root and shoot development in the weeds’ earliest growth stages. Rainfall or irrigation typically brings the chemical down into the soil, where it blocks the enzymatic pathways weeds need to survive. Applied properly, it leads to stronger stands of corn, soybeans, and peanuts. Over the decades, agricultural extension programs have highlighted its strengths: long soil activity, broad weed coverage, and a tendency to complement other herbicide modes of action. Farmers appreciate how dependable metolachlor can be, especially where resistance eats away at older weed control tools.
Metolachlor’s chemical formula is C15H22ClNO2, which says a little about the structure, but the nitty-gritty is that it’s a liquid at room temperature, light yellowish, and has a faint odor. In labs and fields, it’s considered relatively stable when stored correctly, and it mixes well with water, meaning that standard application equipment can handle it just fine. Its crystalline or oily form comes down to purity and handling. Knowing melting and boiling points matters less for farmers and more for those in the formulation and transport business, but every safe shipment and reliable field batch owes something to those technical benchmarks.
Anyone who’s had to read a chemical label knows the legal and safety jargon involved. With metolachlor, the label spells out crop-specific rates, buffer zones from water bodies, reentry intervals, and mixing instructions. Regulators watch the cumulative use and impact, especially because residues hit water sources if not managed carefully. The U.S. Environmental Protection Agency and similar bodies outside North America continue to monitor environmental samples and adjust rules if new evidence comes out. From my experience on the ground, skipping a careful read of the label never pays off if you want to keep your land and neighbors safe.
Production of metolachlor relies on several steps—nucleophilic substitution and acylation come into play, all starting from aniline derivatives. These processes call for significant chemical expertise and careful quality control. Inside factories, batch reactors and separation columns churn for hours to bring the product up to registration standards. Alterations in manufacturing often aim to dial back environmental impact or bump up active ingredient purity, rather than starting from scratch with a whole new process. Sometimes, manufacturers tweak the formula for regional needs, but the backbone remains consistent for decades.
Researchers didn’t stop at the original formula. Chemists have created analogs and substitutes, trying to get the right balance between effectiveness and lower toxicity. The introduction of S-metolachlor—one of the stereoisomers—meant users could get the same weed control using less chemical per acre. This switch played out in the field with reduced application rates and, at times, lower user risk. Chemical modifications like these offer real-world outcomes: reduced runoff potential, slower resistance buildup, and possible improvements in how long the product stays active.
The original “metolachlor” is listed in some places as 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide, though you see plenty of trade names thanks to the way chemical patents and registrations work. In the U.S., generics and proprietary brands pop up in farm catalogs, and many countries allow slightly different registration portfolios. Synonyms help researchers find studies and regulatory guidance, but in the end, if the label includes “metolachlor,” it’s still the same chemical backbone farmers count on.
People working with metolachlor wear gloves, goggles, long sleeves—standard protective gear, because skin and eye contact needs to be avoided. Anyone who’s worked through a spray season knows the importance of keeping up with equipment checks and following cleanup instructions. Training matters both in big ag outfits and on smaller family farms. Early on, there were incidents where improper handling caused short-term sickness. Rules and best practices stepped up quickly, lowering accident rates, but continuous education and access to safety equipment stay just as important.
Walk into any agricultural county in the U.S. corn belt or Brazil’s soybean heartland and growers know metolachlor by reputation. It’s a standard pre-emergent solution for row crops, and its use even reaches specialty vegetables in some regions. The herbicide proves its value where growers aim for clean seedbeds and minimal hand weeding. Over time, weeds adapt, but farmers rotate metolachlor with other herbicides to slow down that resistance process. Its place in tank mixes, field rotations, and integrated weed management strategies shows how thoroughly it’s woven into the backbone of global agriculture.
Research into metolachlor keeps rolling, spurred by the need for sustainable farming and regulatory scrutiny. Soil scientists look at degradation rates, toxicologists review impacts on non-target species, and water quality experts flag runoff points in vulnerable regions. New sensors and analytical techniques pull more data from smaller concentrations, so regulations and recommendations get more precise each year. Collaboration across university extension offices, independent labs, and government agencies helps balance farm productivity with environmental stewardship. That close connection between researchers and growers steers new practices and, sometimes, shapes which chemical tools stay on the market.
Historical reviews pegged metolachlor as moderately toxic if swallowed or inhaled, with limited chronic effects noted in regulatory summaries. Long-term wildlife studies watch how trace amounts affect aquatic creatures and soil biology. Farmers keep an eye on new findings about groundwater or food residues, knowing that stricter residue limits can shift which crops they plant or how they time their fieldwork. International agencies continue updates to risk profiles, and every season brings tweaks to application recommendations or maximum residue limits. Over the years, appeals for clearer residue research keep making headlines, especially where water supplies are tight.
Metolachlor’s path forward depends on more than crop yields. The growing pressure for greener, safer, and more accountable chemical tools means future versions may look different—lower use rates, more targeted application, or quicker breakdown. Farmers today talk with consultants not just about weeds, but soil health and sustainable rotations, expecting herbicides to fit into a bigger puzzle that includes cover crops, buffer strips, and digital farm monitoring. Investment in new chemistry, regulatory oversight, and field adaptability means the next era of weed management may lean on the lessons metolachlor taught the world, even if the product itself gets phased out. Watching how this transition unfolds, from regulators to research labs to rural fields, will shape what choices the next generation of growers gets to make.
Walk by a corn or soybean field in the Midwest, and you’ll probably see the results of metolachlor’s work, even if you don’t realize it. Metolachlor is a pre-emergent herbicide. Farmers use it to stop weeds before they break through the soil. Nobody enjoys hand-weeding a few thousand acres, so chemicals like this have become the backbone of large-scale agriculture.
Metolachlor targets annual grasses and some broadleaf weeds, attacking them as they germinate. It blocks a key enzyme in the seedlings, stunting the roots and shoots before the plant ever grows above ground. Soil application comes before the main crops sprout, so the prized crops like corn, soybeans, cotton, peanuts, and sorghum get a head start over the competition.
I’ve seen farmers breathe a little easier because of this. Weeds steal moisture, shade crops, and siphon off fertilizer. In tight seasons, they can decide whether a farmer makes it to the next. Metolachlor gives the crops a fighting chance, especially in wet springs where weeds come up fast and furious.
Some worry about how long these chemicals stick around. Metolachlor does wind up in groundwater, especially in regions with heavy rainfall and sandy soils. The U.S. Geological Survey detected it in both streams and groundwater, particularly in areas with lots of row cropping. That has led states and the EPA to watch its use closely. Drinking water contamination reports and questions about hormonal disruption in animals keep the discussions about safe farming alive.
Farmers face a tough balance here. Growing up around these fields, I heard a lot about stewardship. No one wants herbicide in their well or in the river. Today, buffer zones and new planting practices cut down on runoff. Low-dose formulas and precision sprayers, especially on GPS-guided tractors, help keep chemicals like metolachlor exactly where they’re needed and no further. There’s always room for improvement, but most growers take the risks seriously.
Every chemical, including metolachlor, faces constant review. The EPA and other agencies push for new data every few years. In some places, alternatives or restrictions phase in whenever there’s evidence of harm. Newer products aim to be more selective or break down faster. Integrating cover crops, rotating chemistry, and mixing in non-chemical methods all help slow down weed resistance.
The debate about herbicides like metolachlor reflects bigger choices about farming and food production. Growing the food people need without runaway weeds creates pressure to use strong tools, but those tools bring responsibilities. The answers keep evolving with new technology, research, and close attention from both the people on the tractors and those pouring glasses of water at home.
Metolachlor helps farmers manage weeds before corn, soybean, and other crops pop up. Walking through farmlands in the Midwest, I’ve seen the green carpets it protects and talked to folks relying on tools like this. Most people won’t touch, mix, or spray the compound, but if you eat, drink, or breathe, bits of farm chemicals can work their way into your daily life.
Let’s not sugarcoat this topic. Studies show metolachlor can drift off fields and collect in surface and groundwater. One review from the US Geological Survey found the molecule in streams, rivers, and even some wells—sometimes above the limits set for safety. People worry about drinking water for good reason. Lab research on rodents links high metolachlor doses with liver and blood changes. The EPA calls it a possible human carcinogen, a title earned after animal studies suggested tumor links. That kind of tag means scientists haven’t proven the danger for humans, but they’ve seen enough signals to take it seriously.
Livestock and pets might meet metolachlor if they drink puddles in treated fields or nibble on contaminated plants. At typical exposure levels, acute poisoning isn’t likely, but long-term effects remain in debate. Reports from the field mostly mention skin and eye irritation when workers handle the concentrated material.
Safe use comes down to how much and how often people and animals contact this pesticide. One farmer in Iowa explained that after applying metolachlor, he keeps animals out of the fields for days. Neighbors sometimes worry runoff will affect their backyard chickens or even pets drinking from creeks. In rural clinics, doctors rarely see direct metolachlor poisoning. Instead, they field questions about chronic exposure and the possible risks for families on well water.
City dwellers face less direct exposure, but metolachlor doesn’t always stay put. After heavy rains, herbicides run off into water supplies. Take the case of Des Moines, where the drinking water utility sometimes struggles to filter out chemicals after storms. The science on low-dose, long-term effects stays murky, yet the presence alone makes people uneasy.
A cleaner future means less routine dependence on chemicals like this one. Some growers now rotate crops to keep weeds in check, cutting the need for metolachlor. Others invest in buffer strips—bands of grass and trees along streams—so runoff moves slower and filters out more residues. A few have begun working with soil health coaches who encourage less chemical input, better timing, and safer storage.
Testing wells and streams more frequently helps flag problems before they land in kitchens. Push for better labeling and safety briefings at local farm-supply shops goes a long way in protecting workers and neighbors alike. On my visits to ag extension offices, I often see folks trading tips on protective gear and sharing updates on safer alternatives.
People need facts to make smart choices for their families and livestock. Transparent reporting from water utilities, clearer farm-to-table records, and better research funding all build trust. Scientists continue testing new weed solutions—some are already helping reduce the footprint of old chemicals. The question of absolute safety never quite gets put to bed, but new knowledge can steer communities toward healthier soil, safer water, and a clearer path for everyone living and working in farm country.
Using metolachlor on a farm isn’t just about pouring a jug into a sprayer and hoping for the best. There's an art in pairing knowledge of chemistry with an understanding of the land. Farmers know metolachlor as an herbicide valued for weed control in crops like corn, soybeans, and cotton. I’ve watched growers shape entire schedules around its use, especially in those early days after planting, when tiny weed shoots threaten to overrun young crops. The trick lies in blending timing, weather, and soil condition.
Apply metolachlor right after planting and before weeds have time to get established. Waiting too long gives weeds a foothold, forcing heavier doses or risk of losing yield. Some years, a rain shower the day after application worked wonders, helping the product move into the topsoil where weed seeds germinate. In dry spells, irrigation pulls double duty: feeding thirsty plants and activating the chemical barrier among the soil particles.
Soil isn’t just dirt—it’s a complex world of minerals, microbes, and organic matter. Heavy clay holds herbicides near the surface, while sandy soil lets them slip deeper. If the ground contains a lot of organic material, metolachlor binds up faster, sometimes enough to require adjustments up in the application rate. Lab numbers show metolachlor tends to stick tight to organic matter, so knowing what your field is made of makes a big difference.
Misuse impacts more than just a field’s crop. Metolachlor can move with rainwater, especially on steep or bare ground, leading to runoff into streams. The EPA keeps a close eye on this, pushing for buffer strips and application setbacks near water. Responsible farming means thinking beyond the field border. A buffer of natural vegetation goes a long way in holding back both weeds and chemicals, safeguarding both neighbors and wildlife.
Precision wins every time. Some of the worst trouble I saw came from hasty mixing: too strong and plants burned; too weak and the weeds won. Take the time to calibrate the sprayer and stick to the recommended rate—usually about one to two pints per acre, but always double-check the label. Overlapping passes or making extra trips across wet patches just wastes money and ups risk of runoff.
Wearing protective gear gets overlooked when the pressure’s on. I’ve seen neighbors with rashes and headaches after splashes or wind drift. Gloves, long sleeves, and a sprayer in good shape cost a fraction of a hospital visit. Washing up right after handling herbicide comes as second nature after handling drums year after year.
People talk about integrated weed management, meaning don’t lean on chemicals alone. Crop rotation and cover crops team up with metolachlor to cut back resistance and save money in the long run. Some growers even track which fields struggle more with weeds, reserve metolachlor for those hotspots, and go lighter elsewhere. Newer technologies—like GPS-guided equipment—cut down overlap and reduce the amount hitting non-target zones.
Putting metolachlor to work involves judgment, observation, and a willingness to learn from results each year. The land rewards care and attention, and, in my experience, so does the bottom line. Balancing control, safety, and stewardship might not come easy, but it brings long-term benefits for families, food, and the environment.
Growing up in rural Illinois, spring always brought tractors, seed drills, and the familiar sweet-earth smell of freshly broken ground. Every season, my family faced the parade of stubborn weeds: pigweed, foxtail, and lamb’s quarters fighting to choke out the hopeful shoots of corn and beans. It’s the kind of annual battle you can’t opt out of if you want a harvest come fall. Metolachlor, a pre-emergent herbicide discovered in the mid-1970s, quickly won wide use across the Corn Belt for its knack at stopping those weeds before they grabbed a foothold.
Metolachlor has earned its place especially with corn and soybeans. These two crops take up a big piece of American farmland, and both struggle with grass and some broadleaf weeds early in the growing season. This herbicide goes down before or just after planting, forming a protective barrier in the upper soil layer. Metolachlor’s ability to control nutsedge, barnyardgrass, and crabgrass fits squarely with what these crops need at their most vulnerable stage.
Fields growing cotton and peanuts have also gained from the use of metolachlor. In the South, with humid summers and persistent weed pressure, farmers lean on it to protect the young crops. Cotton seedlings, for example, are slow starters and lose ground fast if weeds get tall. Applying metolachlor buys time for those plants to outpace early-season invaders. The same logic holds for peanuts, a specialty crop facing rigid economic margins and no room for handweeding.
Looking beyond row crops, sorghum and sunflowers sometimes see metolachlor, too. The chemical’s selectivity works out for these, giving control over unwanted grasses while leaving the crop undisturbed. Even vegetable crops such as tomatoes and potatoes have received limited use, though only in specific areas and with tight label restrictions. That highlights the product’s careful fit: not every crop tolerates it, and not all soils or climates play nicely.
Decisions around herbicides can’t just hinge on cost or convenience. Safeguarding drinking water and soil health sits right next to weed control in the real world. The US Geological Survey measured metolachlor in some waterways near farm country, raising sensible discussion about runoff and persistence. That kind of reality check matters. Farmers now often use precision sprayers and soil testing to limit overapplication and target problem spots, reducing runoff and drift.
Responsible stewardship shapes the future of these chemicals on the landscape. Universities and extension services continue to study metolachlor’s behavior in regional soils and its effect on non-target organisms. Some areas restrict timing or buffer zones near water. These steps all come from one lived truth: farmers and rural communities depend on healthy fields and streams not just for one season, but for every season to come.
With weeds evolving resistance and markets shifting, relying on a single herbicide feels like gambling the future. Old-timers remember the days before pre-emergents, when cultivators and hoe crews did the work. Now, most growers rotate chemistry, apply cultural practices—like varying planting dates or cover cropping—and use scouting to keep solutions flexible and grounded in field observations. Blending old experience with new tools creates room for every family’s land to stay productive, healthy, and profitable.
Metolachlor shows up in farm news each year, especially in regions that grow a lot of corn, soybeans, or cotton. It belongs to the group of herbicides known as chloroacetanilides. Farmers count on this chemical to knock down grasses and weeds before they can steal nutrients from crops. Its popularity is no accident; it has helped drive up yields and make food more plentiful. Still, the convenience that comes from reaching for metolachlor also brings along some baggage—especially for people who care about clean water, healthy soil, and resilient ecosystems.
Anyone who grew up near farm fields has likely seen runoff in spring. Metolachlor doesn't break down quickly in water, and the soil can only hold so much before rain washes it away. Testing in rivers from the Midwest to the South often turns up traces of this chemical long after the corn’s been harvested. Research from the U.S. Geological Survey shows metolachlor sticks around in both surface water and groundwater. It's been spotted in drinking water in rural areas, raising questions about the long-term effects on people and pets.
Where metolachlor finds its way into aquatic systems, it creates problems for the creatures that live there. Frogs, fish, and insects all depend on clean water for survival. Lab findings point to reduced growth in amphibians and changes in fish reproduction even when metolachlor shows up at low levels. These animals already face plenty of challenges—from habitat loss to extreme weather—and another threat from farm chemicals makes things even tougher. Misplaced confidence in what's invisible means we don't notice these changes until something obvious, like a frog population crash, happens.
Soil isn’t just dirt—it’s a living network of fungi, bacteria, insects, and plant roots. This life builds the backbone for sustainable farming. Metolachlor can trip up some of the helpful microbes, knocking soil out of balance. Researchers from universities in Iowa and Illinois have highlighted shifts in soil biology. Those microbes play a big role in recycling nutrients, keeping pests in check, and building up resilience against disease. If their numbers or diversity drop, soil may end up brittle and less able to hold onto fertilizers and water.
There are paths toward progress. Precision farming offers an answer because new GPS-guided tools let growers apply herbicides only where weeds actually threaten crops, sparing the bulk of a field. Buffer strips—bands of grass and trees between cropland and waterways—work like filters, grabbing chemicals before they can reach streams. More farmers have started using cover crops: plants like clover or rye that grow between seasons, holding soil in place and outcompeting weeds naturally.
Regulators and industry groups need to take farm runoff as seriously as air or automobile pollution. Some communities have already called for limits on metolachlor, especially where water samples keep testing positive. Costs may go up at first, but safer drinking water and revived local wildlife matter too. With smart planning and a look at the bigger picture, those who grow our food can protect both their land and the life around it.
| Names | |
| Preferred IUPAC name | 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide |
| Other names |
Dual Pennant Bicep CGA-24705 Metolaclor Cylan Me-too-lachlor |
| Pronunciation | /ˌmiːtəˈlæk.lɔːr/ |
| Identifiers | |
| CAS Number | 87392-12-9 |
| Beilstein Reference | Beilstein 1911591 |
| ChEBI | CHEBI:41052 |
| ChEMBL | CHEMBL333110 |
| ChemSpider | 57952 |
| DrugBank | DB02366 |
| ECHA InfoCard | 068875e6-d6dd-4b22-b7df-c6f0f6b1689e |
| EC Number | 262-967-7 |
| Gmelin Reference | 95833 |
| KEGG | C11206 |
| MeSH | D016507 |
| PubChem CID | 5373209 |
| RTECS number | SY1575000 |
| UNII | 4M6712XG89 |
| UN number | UN3082 |
| Properties | |
| Chemical formula | C15H22ClNO2 |
| Molar mass | 283.8 g/mol |
| Appearance | Light yellow liquid |
| Odor | Odorless |
| Density | 1.11 g/cm³ |
| Solubility in water | 530 mg/L |
| log P | 3.00 |
| Vapor pressure | 2.5 × 10⁻⁵ mmHg (25°C) |
| Acidity (pKa) | pKa = 2.9 |
| Basicity (pKb) | pKb = 12.6 |
| Refractive index (nD) | 1.521 |
| Viscosity | Viscosity: 0.306 mPa·s (25 °C) |
| Dipole moment | 3.25 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 354.6 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -265.6 kJ·mol⁻¹ |
| Std enthalpy of combustion (ΔcH⦵298) | -6535 kJ/mol |
| Pharmacology | |
| ATC code | S01XA22 |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes skin and eye irritation. May cause allergic skin reaction. Suspected of causing cancer. Toxic to aquatic life with long lasting effects. |
| GHS labelling | GHS02, GHS07, GHS08, GHS09 |
| Pictograms | GHS02,GHS07,GHS08 |
| Signal word | Warning |
| Hazard statements | H302, H315, H317, H319, H361fd, H373, H410 |
| Precautionary statements | P201, P202, P261, P264, P270, P271, P272, P273, P280, P281, P301+P312, P302+P352, P304+P340, P308+P313, P314, P333+P313, P337+P313, P362+P364, P391, P405, P501 |
| NFPA 704 (fire diamond) | 2-1-0 |
| Flash point | 100 °C |
| Autoignition temperature | 650°C |
| Lethal dose or concentration | Oral LD50 (rat): 1,200 mg/kg |
| LD50 (median dose) | LD50 (median dose) of Metolachlor: "1,200 mg/kg (rat, oral) |
| NIOSH | SNF61270 |
| PEL (Permissible) | PEL (Permissible Exposure Limit) of Metolachlor: 10 mg/m³ |
| REL (Recommended) | 0.5 |
| Related compounds | |
| Related compounds |
Acetochlor Alachlor Butachlor Dimethenamid Propachlor |
