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2,4-D is a selective systemic plant growth regulator herbicide primarily used for post emergence broadleaf weed control (for example: waterhemp, ragweed, horseweed) in a variety of crops grass (monocot) crops, including corn, small grains, sorghum, grass pastures, and 2,4-D tolerant soybeans. It is also used for weed control in turf such as residential lawns, sports fields, parks, and other areas. 2,4-D is Site-of-Action 4, synthetic auxin herbicide which is a type of growth regulator herbicide.

2,4-D has long been used in agricultural and nonagricultural herbicide products. The United States Environmental Protection Agency (EPA) has approved post-emergence use of two 2,4-D products, Enlist Duo (EPA Reg. No. 62719-649, DowDuPont) and Enlist One (EPA Reg. No. 62719-695, DowDuPont), on 2,4-D-tolerant (Enlist) corn and soybeans.

In Minnesota, waterhemp has evolved resistance to several herbicide classes (for example: glyphosate, ALS, PPO herbicides). These new 2,4-D products are approved for use in Enlist corn and soybeans to control herbicide-resistant weeds such as waterhemp. Also, palmer amaranth, Amaranthus palmeri, another aggressive species in the pigweed family has been found in a few Minnesota fields in recent years. Populations of this weed with resistance to glyphosate, ALS, PPO, and HPPD herbicides have been identified in other upper-Midwestern states.  

For more information on Palmer amaranth identification see the University of Minnesota Extension Minnesota Crop News, Be on the lookout for Palmer amaranth

2,4-D is a volatile chemical that may damage non-target plant species through spray drift and/or volatilization (vapor drift) or misapplication. Misuse of 2,4-D products may cause serious damage to sensitive plants species including non-2,4-D-tolerant crops like grapes, trees, ornamentals, etc. Some species are extremely sensitive to 2,4-D and show injury from low very low exposure.

The MDA requires 2,4-D product users to carefully read the labels and adhere to all label requirements and restrictions. The EPA granted a registration for Enlist One and Enlist Duo herbicides, but with additional restrictions. Label changes include:

• Application timing on Enlist soybeans changed from “through growth stage R2” to “through growth stage R1” (R1 = beginning flowering). This is to prevent application when crops are in bloom and may attract pollinators.
• Enlist product application is prohibited when rainfall is expected to occur within 48 hours and when soils are saturated or at field capacity.
• Irrigation within48 hours of application is prohibited.
• The product labels may require land managers, applicators and users of these products to implement land management practices (Mitigation Measures) based on hydrologic soil groups to reduce runoff. More information can be found on the manufacture's website listed on the label, Enlist Mitigation Measures to Manage Runoff.

The restriction for application to Enlist corn remains - Apply when corn is no larger than V8 growth stage or 30 inches (free standing) tall, whichever occurs first. Applications to corn with drop nozzles to avoid spraying into the whorl can be made to 30 to 48 inches plants.

Also, all applicators must follow the requirements specified in the Minnesota Pesticide Control Law.

The MDA encourages the reporting of all suspected or known 2,4-D damage. You can file a formal complaint by calling 651-201-6333 between 8:00 a.m. and 4:00 p.m. Monday through Friday or by completing an online complaint form. For more information, refer to the pesticide drift complaint process and timeline.

The labels of new 2,4-D products strictly prohibit the preemergence or postemergence use of old 2,4-D products on Enlist corn and soybeans. 2,4-D products that do not contain COLEX-D Technology are not approved for use with Enlist crops. Carefully read and follow all label requirements. 

Other 2,4-D products (LV4 ester, amine, etc.) can be applied preplant to Enlist crops, but must adhere to the required preplant intervals. Also consider herbicide resistance selection pressure from multiple applications of the same active ingredient in the same season.