Regulatory History of 2,4-D
2,4-D has been commercially available for 70 years, and regulators continue to say it can be used safely according to label directions. An extraordinary amount of data supports its continued registration. That data has been rigorously evaluated and re-evaluated. Global regulatory agencies have consistently found the compound to pose no danger to human health when used according to label directions.
1“2,4-D remains registered globally with registrations in more than 90 countries. After decades of use, 2,4-D is still the third most widely used herbicide in the United States (USEPA 2015).”
Economic Benefits of 2,4-D
Without 2,4-D, applicators would need to switch to more expensive alternative herbicides and would likely result in decreased crop yields. An extraordinary amount of data supports its continued registration. That data has been rigorously evaluated and re-evaluated. Global regulatory agencies have consistently found the compound to pose no danger to human health when used according to label directions.
“2,4-D remains registered globally with registrations in more than 90 countries. After decades of use, 2,4-D is still the third most widely used herbicide in the United States (USEPA 2015).”
Pastureland, Rangeland, Alfalfa Forage, and Invasive Weeds
2,4-D is an important tool for weed control in pastureland, rangeland, and alfalfa forage. Losing it would mean increased cost for producers both small and large. To manage noxious or invasive species, between 11 and 20 million pounds of 2,4-D are applied annually.
“Over half of the United States’ land area consists of pastures, rangeland, alfalfa, or natural areas. Any scenario without 2,4-D would significantly increase costs to applicators, and increase the negative effects of weeds and noxious or invasive plants across the United States.”
Field Corn, Soybean, Sorghum, and Peanuts
Weeds are less likely to become resistant to 2,4-D, making it an integral part of weed control in high intensity crops like corn and soybean. 2,4-D is inexpensive and effective, particularly for producers of low-acreage crops where new herbicides are not being developed. The loss of 2,4-D would significantly hinder production for these producers.
“Farmers and regulators alike are striving to reduce tillage…[and] if phenoxy herbicides were no longer available, growers may need to respond by increasing tillage”
Turfgrass in the United States
The use of 2,4-D on turfgrass was one of the first uses of the selective herbicide. 2,4-D is the most commonly used herbicide for turfgrass weed control in the combined industrial/commercial/governmental sector, with applications in 2007 totalling between 19 and 22 million pounds. Applications of 2,4-D in the home and garden sectors totalled between 8 and 11 million pounds.
2,4-D is an inexpensive and effective tool for weed control and herbicide resistance management in small grains. 13.4 million acres of winter wheat alone were treated with 4.04 million pounds of 2,4-D in 2012, demonstrating the utility of the herbicide. Alternative herbicides are either less effective or more expensive, while manual weed control is astronomically more costly and difficult due to planting practices in small grains. On a per acre basis, no herbicide controls as many weeds as inexpensively as 2,4-D.
Flax, Millet, Rice, Wildrice, Seed Crops, Sugarcane, Pea, and Fallow
2,4-D and MCPA provide effective and economical control of a very wide range of broadleaf weeds. 2,4-D serves an important role in control of resistant weeds and development of resistance management programs. Some crops have very few alternative herbicide options for postemergence broadleaf weed control.
Orchard,Vineyard, Hops, and Soft Fruit Production
The loss of 2,4-D could cause significant economic and production challenges in some tree, vine, and fruit crops. 2,4-D has a unique fit in production systems that use grass cover crops between or within the rows of perennial fruit and nut plants. No other available post-emergence herbicide can provide the same level of broadleaf weed control without causing significant damage to grass cover crops. 2,4-D isopropyl ester can be used at very low rates as a growth regulator on some citrus crops.
2,4-D is the second most widely used herbicide for integrated vegetation management on rights-of-way across the United States, with 6.3 million lbs sold for such uses in 2013. It is estimated that there are 11.9 million acres of roadway right-of-way alone across the United States, with 77% of them being treated with herbicides. 2,4-D is effective and inexpensive; it controls problem broadleaf weeds while leaving desirable grasses unaffected.
2,4-D is an inexpensive and effective option for controlling problematic aquatic weeds such as Eurasian watermilfoil. Before serious management programs were implemented there were over 500,000 acres of water hyacinth in just two states, Florida and Louisiana. Were 2,4-D unavailable, states would have to either increase their budgets for aquatic weed control by a factor of 13, or drastically reduce the acreage they treat.
2,4-D sees less use in vegetable production than other crops, but remains an important tool, largely for its ability to manage weeds that have become resistant to other herbicides. Loss of access to 2,4-D in asparagus crops would have a net loss of $6-8 million per year. Alternative herbicides remain significantly more expensive than 2,4-D.
Cotton is a significant industry in the United States, with revenues exceeding $120 billion and product values over $35 billion. With new technology, 2,4-D is set to become an effective tool for fighting herbicide resistant weeds in cotton crops. Glyphosate-resistant weeds have, in some cases, forced farmers to return to manual weeding practices, at great expense.
Herbicide Resistance Management
There are 33 different weed species in the United States that are resistant to one or more herbicide mechanisms of action. Of these resistant species, 25 are effectively controlled by 2,4-D. After more than 70 years of use, only 7 species of weed have become resistant to 2,4-D, leaving it as an effective tool for managing weeds resistant to other herbicides.
Formulations: Amine and Esters
2,4-D is generally formulated as an amine salt or an ester, each of which have their own advantages and tradeoffs. Generally, ester formulations are considered more efficacious, but more likely to drift off target, while amine salts are considered less efficacious but more stable. Some phenoxy herbicides can be used interchangeably, but others cannot.