Hurdling Changes in Dicamba Use in the 2020 Growing Season

July 6th, 2020

There’s an easy way to avoid wasting your time and money —read the label on your dicamba products every single time before mixing it in the tank. It’s not only the law, but a misuse could cost you your yield and your profits. This year, added regulatory changes make it even more complicated and more important for farmers to understand the regulations for dicamba use.

Changes in Regulation

Following the label when applying herbicides is a crucial piece of pesticide management, especially with recent uncertainty surrounding dicamba herbicides formulated for post-emergence application in tolerant soybeans. Labeled requirements are designed to avoid off-target movement that could result in crop injury. This is especially true when spraying dicamba products for post-emergent control of weeds in soybeans or corn.

The U.S. Court of Appeals for the Ninth Circuit vacated the registrations for three dicamba herbicides: XtendiMax (Bayer), Engenia (BASF) and FeXapan (Corteva Agriscience) in June 2020. The Environmental Protection Agency responded by issuing a cancellation order that allows farmers to use existing stocks of dicamba in their possession on June 3 this season under specific conditions. The order, including its existing stock provisions, was upheld by the appeals court. Farmers and commercial applicators may use existing stocks of the affected dicamba formulations according to the original label approved in 2018 until their state’s cutoff date or by July 31, whichever comes first. More details on this action and what it means are available via the Take Action program’s dicamba update.

Minimizing Potential Resistance

Following the label also minimizes the potential for herbicide-resistance development —a problem many farmers across the U.S. face in their fields. Following labels and adopting good management practices help lessen the impact of resistant weeds in farmers’ fields.

Dicamba, a synthetic auxin herbicide, is frequently used to control broadleaf weeds in the field before emergence. In recent years, post-emergence use has increased with the introduction of dicamba-tolerant soybean varieties. In post-emergence applications, it is crucial the products are only applied on dicamba-tolerant crops by following the labeled guidelines and local restrictions.

Dicamba is a valuable tool for managing broadleaf weeds, and it is a selective herbicide for all broadleaf plants. It does not discriminate and can harm susceptible crops, if exposed. Following the label and local restrictions can minimize or prevent spray drift and volatilization, which can have serious repercussions for neighboring crops.

Christy Sprague, extension weed specialist at Michigan State University, said although the labels are long and complex, farmers and applicators should still review all guidelines on the label. As you read through the label, look out for sprayer setup guidelines, tank-mix dos and don’ts, and requirements for the application environment. Applying herbicides off-label raises the risk of resistance development, along with many other potential issues. Luckily, many labels offer some firsthand tips for tackling weeds without increasing herbicide resistance in your fields.

In addition to the label, it’s crucial that farmers know their local and state restrictions and have completed the required applicator training. Farmers interested in finding their state and local regulations can visit the National Pesticide Information Center here.

“Farmers should know the label and local restrictions, and be conscious of guidelines and always be aware of their surroundings,” Sprague said. “This is the best way to manage weeds in the field.”

Best Management Practices

But reading and understanding the label isn’t the only crucial step in applying dicamba. There are several management practices to follow to effectively kill weeds and reduce the chances of mistakes. Those interested in more in-depth information about dicamba’s best management practices can also review the “Managing 2,4-D and Dicamba in Enlist E3 and Xtend Soybeans” fact sheet produced by Take Action. Farmers can take these precautions for the best outcomes:

Check the weather. Wind, rain, temperature and humidity all factor into the success of application. Those applying dicamba should be mindful of wind speeds, heavy rain, high temperatures and low humidity. Lastly, farmers and applicators should follow the time-of-day restrictions and avoid making applications during weather patterns that cause temperature inversions.
Observe buffers. Farmers and applicators should maintain the required distance when spraying near sensitive areas that are downwind. Some state regulations on buffer distances are stricter than the EPA’s, and applicators must follow the most restrictive regulations that apply to the field.
Follow the correct sprayer setups. Farmers and applicators should ensure their nozzles are approved for the herbicide they are applying. They should also be checking their gallons-per-acre application requirements, the minimum and maximum rates per application, sprayer speed limits and boom height requirements.
Know tank-mix restrictions. Applicators should refer to each product label’s website or page to find approved adjuvants, drift reduction agents and other herbicides to mix with Engenia, XtendiMax, FeXapan or Tavium.
Make timely applications. Don’t spray weeds that are too large. It’s important to note over-the-top application of dicamba is prohibited on soybeans later than 45 days after planting.
Use full rates. Partial rates are less effective in solving weed issues and contribute to resistance. Farmers should use full rates to ensure an effective application and delay the onset of resistance.
Clean the entire sprayer properly. With so many herbicide-tolerant traits available, properly cleaning out the spray tank and other sprayer components is crucial to avoid contamination when switching between herbicides and crops. Each label has specific steps for cleaning the sprayer.

Damage was Done —Now What?

An accidental misuse of dicamba can have a detrimental impact on susceptible plants. Damaged plants typically show leaf cupping and puckering on new leaves. And recovering from the injuries is challenging.

Brandon Kerwin, farmer and sales agronomist for Wilbur-Ellis in northeast Kansas, said there are a few ways farmers can handle crop damage due to dicamba.

“The biggest thing is to make sure you keep all of your spraying records,” Kerwin said. “Applicators should also be mindful of what’s in the tank —everything should be an approved tank-mix partner. If it’s not, applicators can get in even more trouble.”

Take Action has a fillable PDF available to track pesticide application.

If you have those items in order, Kerwin said the next step is to contact your chemical provider.

“I would suggest an applicator call their chemical provider and ask to bring a chemical rep to the field. They will then be able to assess the damage and see if the plant is completely killed,” he said. “If you have killed the plant, I’d suggest taking the field to harvest and then compare the yield difference between the damaged sections and the non-damaged sections.”

Kerwin said if there is any damage to a crop such as a fruit tree or vegetable garden, the farmer should consider talking to their local agronomist to help come up with a solution.

If an applicator sprays dicamba and causes damage to a neighbor’s field, Sprague recommended contacting the farmer whose plants show signs of damage.

“Unfortunately, there’s nothing that can be done to rectify the situation because you can’t treat the plant differently. However, I still think the best thing to do is contact that person,” Sprague said.

Farmers should also be mindful of where they are spraying and avoid spraying near sensitive areas, suggested David Lowery, a farmer from Mazon, Illinois.

“There are times I could be on-label, and I still choose not to spray near sensitive areas,” said Lowery. “I have a nursery near one of my fields, and I make sure I am always conscious when I am spraying. I would suggest farmers not push their limits and always be mindful of their surroundings.”

If a farmer suspects they have dicamba-resistant weeds, they should scout fields after application for shifts in weed species and product efficacy. They should also report any incidence of nonperformance to the product registrants at the following numbers:

XtendiMax: 1-844-RRXTEND, 1-844-779-8363
Tavium: 1-866-Syngent(a), 1-866-796-4368
FeXapan: 1-888-6-DUPONT, 1-888-638-7668
Engenia: 1-800-832-HELP, 1-800-832-4357

To delay the onset of dicamba resistance in weeds, an integrated weed management program is necessary. Dicamba and 2,4-D should not be used as post-emergence-only approaches but as part of an integrated residual herbicide program. The Enlist One, Enlist Duo, XtendiMax, Engenia, FeXapan and Tavium herbicide labels mandate scouting for herbicide nonperformance following an application.

Applying Dicamba on Your Fields

In order to use dicamba herbicides, federal regulations require applicators to complete dicamba- or auxin-specific training for the following products:

FeXapan herbicide Plus VaporGrip Technology through Corteva Agriscience.
XtendiMax herbicide with VaporGrip Technology through Bayer.
Engenia herbicide through BASF.
Tavium Plus VaporGrip Technology herbicide through Syngenta.

This year and every year, regulations are updated and changed. Farmers need to make sure they are following their latest state-specific restrictions.

Sprague said some states have implemented new date and temperature cutoffs that will be very location-specific, and some state cutoffs have already passed.

“If farmers are spraying dicamba, it’s important they know what their state regulations are —especially since some states change a little every year,” she said.

Above all, following the label and federal and regional regulations will help reduce the onset of resistance to synthetic auxin herbicides. Farmers and applicators should be following each step and talking with their advisers if they have questions about the label.

Farmers and applicators who are interested in learning more about dicamba and best management practices can review the Take Action fact sheet, “Managing 2,4-D and Dicamba in Enlist and Extend Soybeans,” available here.