ROCKVILLE, Md. (DTN) -- For the fourth time in five years, farmers and applicators face a new set of requirements to spray dicamba over the top of dicamba-tolerant crops.

The stakes for getting it right remain high. Parts of the Midwest and South have seen many consecutive years of off-target dicamba injury to a broad array of crops and plants. This year, dicamba-susceptible soybean acres are projected to increase, as well, with Corteva Agriscience estimating that susceptible Enlist E3 soybeans alone could account for more than 30% of all U.S. soybean acreage in 2021.

In this series of articles called Dicamba Rules Update, DTN explores EPA's changes to new, five-year registrations of three dicamba herbicides: XtendiMax (Bayer), Engenia (BASF) and Tavium (Syngenta). (Corteva has decided not to seek a new registration for its dicamba herbicide, FeXapan.)

Here are the primary areas the series will explore:

1. NEW CUTOFF DATES

For the first time, EPA has established two federal cutoff dates for use of the three dicamba herbicides: June 30 for soybeans and July 30 for cotton.

For Engenia, those cutoff dates are the only spray timing restriction. The XtendiMax label also tells applicators not to spray the product beyond the R1 growth stage in soybeans, and Tavium's label bans applications after V4 in soybeans and the 6-leaf stage in cotton.

However, once again, dicamba cutoff dates will vary by state in 2021. Three states have opted to create more restrictive dates, either by state rulemaking or via relevant state laws. (See more here: https://www.dtnpf.com/…).

As of the time this article was posted, here are the cutoff dates growers may face in the following states:

-- Arkansas: May 25.

-- Indiana: June 20.

-- Illinois: June 20, with an additional 85-degree-Fahrenheit temperature restriction.

Other states, such as Alabama, North Carolina, Mississippi, Oklahoma and Texas are working to develop Section 24(c) special local needs labels to extend the federal cutoff dates to accommodate late-planted soybean and cotton fields. Check with your local state department of agriculture for any local restrictions or additional uses of these three herbicides before spraying.

2. BUFFERS GET BIGGER

The new labels include expanded buffers designed to limit off-target movement. The first required buffer, a 240-foot downwind buffer, is necessary for every dicamba application.

The second buffer requirement is a 57-foot omnidirectional buffer, combined with a 310-foot downwind buffer to protect endangered species. This buffer is only required for fields in counties that have been listed on EPA's Bulletins Live! Two website, because they house federally recognized endangered species.

Do not assume that if a county didn't surface on this website last year, it won't be on the list this year. The EPA has adjusted its listing of counties with endangered species in several states for 2021, and dicamba applicators are required to document that they checked this website before spraying. See it here: https://www.epa.gov/….

Soybean growers have the option of reducing the downwind buffer to 110 feet and the endangered species buffer to 240 feet, if they used a qualified hooded sprayer option that can be found on each product's website (see below).

3. NEW TANK MIX REQUIREMENTS

None of the three newly labeled dicamba herbicides can be used alone; all must be accompanied in the tank with a volatility-reducing adjuvant (VRA) designed to keep the tank mix's pH at or above 5, which research shows lowers the risk of volatility.

If an applicator wants to tank mix other active ingredients, such as herbicides, insecticides or fungicides, with XtendiMax, Engenia or Tavium, they must first check the list of approved tank mix options and determine if it is an approved tank mix partner and if it requires the additional use of a drift reduction agent (DRA).

Applicators can find the approved VRAs, tank mix options and their DRA requirements on each herbicide's website:

XtendiMax: https://www.xtendimaxapplicationrequirements.com/…

Engenia: https://www.engeniaherbicide.com/…

Tavium: https://www.syngenta-us.com/…

4. SAME OLD, SAME OLD

Remember that many parts of the new dicamba labels remain the same. That means only certified applicators can apply the three dicamba herbicides, which remain restricted-use pesticides (RUPs).

Dicamba or auxin-specific training is required annually for all dicamba applicators using these newly labeled herbicides. If your state provides dicamba training sessions, applicators must take those. If your state doesn't offer them, applicators must seek training from the dicamba registrants -- Bayer, BASF or Syngenta.

Due to the pandemic, some states and companies are offering online-only training. See more here: https://www.dtnpf.com/….

Applicators must keep applications within 3- to 10-mile-per-hour wind speeds, at sprayer speeds at or below 15 mph, and with boom height no more than 24 inches above the crop canopy. If the wind is blowing toward a sensitive crop or area, shut the sprayer off.

Dicamba applications are also still prohibited within 48 hours of a heavy rain forecast, as well as during temperature inversions. Spray windows are limited to one hour after sunrise and two hours before sunset.

In addition to checking the Bulletins Live! Two website, applicators are still required to check a sensitive crop registry, such as Field Watch, for each field before applications.

As for tank mixes, AMS (ammonium sulfate) and non-approved nozzles are still banned from use with these herbicides, and triple-rinse cleanout procedures are still required.

Finally, applicators are still required to generate records of all the label requirements within 72 hours of an application and hang on to those records for two years.

For a handy chart that breaks down the changes in the new dicamba labels, see this DTN story here: https://www.dtnpf.com/….

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

Follow her on Twitter @Emily_Unglesbee

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