2,4-D Esters vs Amine Salts
As harvest gets underway, our minds tend to wander to what worked well and didn’t during the growing season and what the plans for next year will be. Weed control is a major part of that cropping plan. Although there are multiple “new” products and product combinations on the market, 2,4-D remains a widely used product.
2,4-D has been used in the United States since the 1940s and is used primarily to control broadleaf weeds in both crop and non-crop acres. It has little efficacy on grasses at recommended rates. There are multiple forms of 2,4-D; however, the mostly widely used in agricultural practices are the ester and amine forms and both have advantages and disadvantages.
Characteristics of Both Formulations
Both major 2,4-D formulations can be used in-crop depending on the label and crop; however, use as a burndown in fall and spring is a primary use.
The ester formulations of 2,4-D have a higher vapor pressure and have the potential to volatilize more than amines. Certain environmental conditions can increase the potential for volatility, such as hot dry weather. Some ester formulations (2,4-D LV6 and 2,4-D LV4) are referred to as “low volatile” esters. These formulations are formulated as long chain esters to make the molecule less volatile.1 Amines are still typically less volatile than even “low volatile” ester formulations.
Amine formulations may provide slightly less weed control because ester formulations are more soluble on the plant’s cuticle. Esters are lipid soluble and move through the cuticle faster than amines which are more water soluble. This allows ester formulations to penetrate the cuticle and get into the leaf more efficiently to eventually interfere with plant growth.
Another difference in the formulations is how well they mix with liquid fertilizer carriers. UAN fertilizer is commonly used as a spray solution carrier in certain burndown and small grain applications. While there can be mixing issues with both formulations, the amine formulation sold is typically more difficult to mix with UAN than the ester formulation because it has a higher tendency to precipitate out of solutions. A jar test can be conducted to determine the compatibility of spray formulations.
What formulation should I use?
Both the ester and amine formulations should be considered if 2,4-D is determined to be an effective herbicide for your weed control program.
For fall burndown applications, the ester formulation may be a better option. Typically, there is less risk of damaging sensitive crops in the fall because environmental conditions are generally favorable and most annual crops have either been harvested or reached maturity. Ester formulations can offer better activity as well.
For spring burndown applications, an amine formulation should be considered due to the reduced risk of volatility. If sensitive crops are emerged and present in the application area, the amine formulation may help limit the risk of off-target movement due to volatility and damage to neighboring crops or sensitive areas.
Neither 2,4-D formulation offers much for soil activity; therefore, alternative or tank-mix products should be considered if residual control is desired or wanted.
Both formulations are labeled for certain in-crop usage in corn, sorghum, and many small grain crops. Always read and follow all label directions and recommendations as far as growth stage and timing when making these applications. Consideration should be made on formulation for these applications as well. As referenced, the ester formulation is typically “hotter” than the amine formulation which can lead to better weed control but can also create a higher potential for crop injury during post emerge applications.
2,4-D continues to be a valuable tool as part of an overall weed management program. Like any program, consideration needs to be made as to weed species, timing, conditions, and tank-mix partners before determining what product is best to use.
1Nice, G., Johnson, B., Bauman, T. 2004. Amine or ester, which is better? WS-31-W. Purdue Extension Weed Science. Purdue University. https://www.panna.org/sites/default/files/2,4-D%20Amine%20or%20Ester%202004-Purdue.pdf.
Web site verified 9/21/21.
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