The other day I got a question from a client regarding the different formulations of 2,4-D, a very common herbicide used widely by gardeners and farmers. I found a great fact sheet from Purdue University which described the differences and is summarized below. It starts out by saying that the amine and ester of 2,4-D are both formulations of one of the oldest and widely used herbicide families, as they were developed in the mid-1940’s by the military for vegetation control. It works as a growth regulator herbicide which induces unorganized growth in the plant which can therefore crush the vascular system of the plant, blocking it off from nutrients, sugar and water.
Used to control annual, biennial, and perennial broadleaf weeds, 2,4-D has little effect on grasses, thus making it the most popular herbicide used in lawns. While it is effective if applied at the correct time, drift can easily occur in non-targeted broadleaf plants due to the result of 2,4-D volatility, its ability to turn into a vapor and move off site. This is how the amine and ester formulations can differ.
Purdue’s publication goes on to summarize that the ester formulation of 2,4-D have higher vapor pressures and tend to volatilize more than amines, therefore one should use an amine formulation when volatilization is a concern with sensitive plants. I always caution people who use 2,4-D that volatility increases in hot, dry weather. When temperatures are above 85 degrees F, only the amine formulations should be used. Ester formulation is more effective at penetrating the leaf cuticle, so amine use rates are usually higher than ester rates to compensate for reduced absorption.
One weed I’ve been receiving several questions on is the purple flower growing in lawns – most likely henbit. It definitely flourished with last year’s drought, but for best control, apply a broadleaf herbicide in the fall. To achieve 90% control of henbit, apply a post emergent herbicide such as Trimec when in the early growth stage. There are several formulations of Trimec which uses 2,4-D as an active ingredient.
In summary, know which formulation you are working with, apply during the most effective time for your target species and adjust rates accordingly. As always, follow label directions and take the proper safety precautions to protect your health. For more helpful information on which herbicides to apply and when, go to UNL Extension’s Weed Guide.