Dicamba is a selective herbicide used to kill broadleaf weeds in crops, lawns, pastures, and other managed landscapes. It has been in use since 1967 and can be found in over 1,100 products sold in the United States, ranging from concentrated agricultural formulations to ready-to-use lawn care sprays.
How Dicamba Works
Dicamba mimics a natural plant growth hormone called auxin. At low levels, auxin regulates normal processes like cell elongation and division. When dicamba floods a plant’s tissues at high concentrations, it triggers abnormal, uncontrollable growth. The plant essentially grows itself to death, with stems twisting, leaves curling, and normal functions shutting down. This makes dicamba effective both before weeds emerge (pre-emergent) and after they’re already growing (post-emergent).
Because dicamba is selective, it targets broadleaf plants while leaving grasses largely unharmed. This is why it works well in corn fields, wheat fields, and grass lawns, where the crop or turf is a grass species and the weeds you want gone (dandelions, pigweed, thistle, and similar plants) are broadleaf.
Major Agricultural Uses
The largest markets for dicamba by volume are corn, cotton, soybeans, wheat, sorghum, sugarcane, pasture, and fallow land. It also sees use on asparagus, barley, oats, hay, and grass grown for seed. In agriculture, dicamba controls annual, biennial, and perennial broadleaf weeds that compete with crops for water, nutrients, and sunlight.
A major shift in dicamba’s role came with the development of genetically engineered, dicamba-tolerant crop varieties. Bayer’s XtendFlex soybeans, for example, are engineered to tolerate dicamba, glyphosate, and glufosinate, three different herbicides. This lets farmers spray dicamba directly over the top of growing soybean or cotton plants to kill surrounding weeds without harming the crop. Before these traits existed, dicamba could only be applied to fields before the crop emerged or carefully directed away from it.
This “over-the-top” approach became especially popular as many weed species developed resistance to glyphosate (the active ingredient in Roundup). Farmers needed another tool, and dicamba filled that gap. The combination of multiple herbicide tolerances gives growers flexibility to rotate or mix products, which helps slow the development of resistant weed populations.
Lawn, Turf, and Non-Crop Uses
Outside of agriculture, dicamba is a common ingredient in consumer lawn care products. You’ll find it in weed-and-feed granules, liquid concentrates, and ready-to-use sprayers designed for home lawns. It’s also applied on golf courses, along roadsides and railways, under utility lines, and on conservation reserve land. In all of these settings, the goal is the same: eliminate broadleaf weeds while preserving grass.
Products containing dicamba come as liquids, dusts, or granules, and they range from professional-grade concentrates to bottles you can pick up at a hardware store.
The Drift Problem
Dicamba’s biggest controversy centers on its tendency to move off-target. The chemical is volatile, meaning it can evaporate from treated fields and travel as a vapor to neighboring properties. This is different from ordinary spray drift, where droplets physically blow sideways during application. With dicamba, the herbicide can volatilize hours or even days after spraying, particularly in warm weather, and drift onto nearby crops, gardens, or trees that aren’t tolerant.
Because dicamba is so effective at disrupting broadleaf plant growth, even tiny amounts reaching a neighbor’s soybean field (if those soybeans aren’t dicamba-tolerant), tomato plants, or fruit trees can cause visible damage: cupped and curled leaves, stunted growth, and reduced yields. This has led to thousands of complaints from farmers and landowners, particularly in soybean-growing regions where dicamba-tolerant and non-tolerant fields sit side by side.
Current Regulations
The EPA has responded to drift concerns by imposing increasingly strict rules on over-the-top dicamba use on cotton and soybeans. The most recent registration includes what the agency calls the strongest protections in its history for this application. Key restrictions for the 2026 growing season cut the maximum annual application rate in half, limiting all dicamba products combined to 1.0 pound of active ingredient per acre per year. Applicators are also required to double the amount of volatility reduction agents they add to the spray mix.
The current approval is time-limited, covering only the next two growing seasons and subject to further review. These label requirements are legally enforceable, and applicators who violate them face significant penalties under federal pesticide law. Older uses of dicamba on lawns, pastures, and other settings have not faced the same level of restriction, since those applications don’t involve the same scale or proximity issues that over-the-top crop spraying creates.
Health and Safety Profile
The EPA classifies dicamba as “not likely to be carcinogenic to humans.” It has low acute toxicity whether swallowed, absorbed through the skin, or inhaled, placing it in the agency’s lower-risk categories (III and IV on a scale where I is the most toxic). It can irritate the eyes and skin on direct contact but is not considered a skin sensitizer, meaning it doesn’t typically cause allergic reactions with repeated exposure.
At very high doses in animal studies, dicamba caused neurological effects like unsteady gait, reduced motor activity, and impaired reflexes. These effects appeared at doses well above what people would encounter through food residues or normal product use. The EPA has set a chronic reference dose of 0.04 milligrams per kilogram of body weight per day, which represents the level considered safe for daily long-term exposure with built-in safety margins. For workers who handle dicamba, the primary exposure concern is inhalation rather than skin absorption.