About two years. That’s all the time you have to prove to the Environmental Protection Agency (EPA) you and your neighbors will follow new dicamba formulation label requirements, or the agency could let its approval expire at the end of 2018. “With the possibility of spraying in June and July on lots of additional acres, remember broadleaf plants are very, very sensitive to dicamba,” says Mandy Bish, senior research specialist at the University of Missouri’s weed science program. “It only takes a small amount to injure non-target plants. That’s the difference between dicamba and other herbicides you’re used to using.”
Dicamba kills susceptible plants by creating a hormone imbalance that interferes with cell division, cell enlargement and protein synthesis, eventually killing the plant. In 2016, more than 200,000 acres were damaged from illegal dicamba use of unapproved, volatile formulations of the herbicide. While new formulations promise reduced volatility, stewardship and following the herbicides’ label are still critical to prove to EPA you can use dicamba ethically long term.
Monsanto, DuPont and BASF offer new over-the-top formulations of dicamba this year. Monsanto’s XtendiMax uses VaporGrip technology to reduce volatility and help minimize drift. DuPont’s FeXapan also uses VaporGrip technology to reduce drift and volatility risks. BASF’s Engenia uses a new salt, BAPMA, to reduce volatility. The labels for these formulations are optimized to protect sensitive crops and include specific requirements to reduce drift risk that could cause damage.
Beware of Off-Target Movement
Drift refers to particle movement while volatility refers to evaporation. Review conventional and supplemental herbicide labels as well as EPA-mandated company websites for application instructions. See state restrictions.
Nozzle Type (see label for other applications and their requirements)
- Engenia: Use only approved nozzles for over-the-top application in dicamba tolerant crops. Only TTI11004 and TTI11005 are currently approved, but check tank-mix website for updates.
- FeXapan and XtendiMax: Apply large droplets with specific nozzles. Don’t use flat fan nozzles that produce driftable fines. Use TTI11004 or nozzles listed on the EPA-mandated product websites.
Spray Volume and Pressure
- Engenia: Don’t exceed nozzle manufacturer’s advised pressures. Lower pressure produces larger drops. When higher flow rates are needed, use large orifice nozzles instead of increasing pressure. Make sure sprayer rate hardware doesn’t allow pressure to increase above allotted range.
- FeXapan & XtendiMax: Spray at least 10 gal. per acre with 63 psi max in TTI11004. Visit EPA-mandated websites for other nozzle information. Use a higher spray volume in dense vegetation.
Equipment Ground Speed
- Stay under 15 mph to reduce drift potential—slower speeds result in better coverage.
Spray Boom Height
- Keep the boom no more than 24" above the target weed or crop canopy (if a weed is 4" tall, then no more than 28" above the ground). The lower the boom is set, the less likely droplets are exposed to wind drift or evaporation.
- Hooded sprayers are optional but can help reduce drift.
- The potential for drift increases during temperature inversions because droplets can remain suspended in the air after application and move off-target when wind speed increases. Watch for situations that increase the risk of a temperature inversion: Evenings and nights with limited cloud cover and little or no wind. Ground fog or smoke that layers and moves laterally in a concentrated cloud. Wind speeds lower than 3 mph.
- Engenia: Do not spray if wind exceeds 15 mph or is less than 3 mph unless you’re sure there is no temperature inversion. Don’t spray if wind is blowing toward neighboring specialty crops or if wind exceeds 10 mph toward sensitive crops. Additional state restrictions might apply.
- FeXapan & XtendiMax: Optimum wind speed is 3 mph to 10 mph. Do not spray if wind speed is greater than 15 mph or under 3 mph. Also, do not spray if wind direction is blowing toward non-target commercially grown sensitive crops.
- Keep a 110' buffer when wind is spraying toward sensitive areas (if rate exceeds 22 fl. oz.per acre use a 220' buffer). Check each product label for additional details. Buffer is between the last treated row and the closest downwind edge of the treated field.
Be Mindful of What, When and How Much Product Can Go in the Tank
Know what you put in the tank can affect drift and lead to crop damage if you’re not careful. Before mixing herbicide or adjuvant products, make sure the tank mix is approved. Visit the web link below to find more information.
- Engenia: Dicamba tolerant soybeans—Max of 12.8 fl. oz. per application and 51.2 fl. oz. per season. Dicamba tolerant cotton—Max of 12.8 fl. oz. per application and 2 lb. dicamba acid equivalent per season.
- FeXapan & XtendiMax: Dicamba tolerant soybeans—Max of 44 fl. oz. per preplant application, 22 fl. oz. per postemergent application and max of 88 fl. oz. per season. Dicamba tolerant cotton—Max of 44 fl. oz. per preplant application, 22 fl. oz. per postemergent application and max of 88 fl. oz. per season.
- Engenia: Dicamba tolerant soybeans—Use preplant, pre-emergent and postemergent applications through R1 up to four applications (two preplant/pre-emergent applications totaling 25.6 fl. oz. and two postemergent totaling 25.6 fl. oz.). Dicamba tolerant cotton—Apply preplant, pre-emergent and postemergent until seven days before harvest.
- FeXapan: Dicamba tolerant soybeans—Apply preplant, pre-emergent and postemergent up to and including R1. Dicamba tolerant cotton—Use preplant, pre-emergent and postemergent applications up to seven days before harvest.
- XtendiMax: Dicamba tolerant soybeans—Use within 28 days or less of preplant and up to two post-emergent applications up to and including R1. Dicamba tolerant cotton—Use within 21 days or less of preplant and up to four day postemergence until seven days before harvest.
Tank Mixing Instructions
Engenia, FeXapan & XtendiMax: Can only be tank mixed with specific products listed on EPA-mandated websites, which have been tested and found to not have an adverse effect on the spray drift properties of the dicamba herbicide formulation the applicator will use.
- Applicators are required to check the list of EPA-approved products within seven days of application. The tank-mix must be on the list of tested and approved products and not prohibited on the label.
- Note some crop oil concentrates, high surfactant oil concentrates and methylated seed oil adjuvants can cause crop response.
- Don’t tank mix products containing ammonium salts such as ammonium sulfate and urea ammonium nitrate.
- Double check with drift reduction agent (DRA) manufacturers to see if approved DRA will work with spray nozzle, spray pressure and spray solution.
Avoid Product Carryover Into Non-Tolerant Fields
If product sits in a sprayer and isn’t thoroughly cleaned, you can damage the next field. Engenia, FeXapan and XtendiMax all suggest similar sprayer cleaning steps:
- Immediately drain the sprayer after use—do not allow the chemical to sit overnight prior to flushing.
- Flush tank, hoses, boom and nozzles with clean water. Open boom ends while flushing.
- Inspect and clean strainers, screens and filters.
- Mix a cleaning solution with detergent or sprayer cleaner.
- Wash all parts of the tank, including inside top surface, agitate the sprayer and recirculate the cleaning solution for at least 15 minutes and remove visible deposits.
- Flush hoses, spray lines and nozzles with cleaning solution for at least one minute.
- Drain pump, filter and lines (according to Engenia label); repeat the above six steps two more times for triple rinse (according to XtendiMax and FeXapan labels).
- Rinse the complete spraying system with clean water (Engenia); after completing above procedures remove nozzles, screens and strainers and clean separately in cleaning solution (XtendiMax and FeXapan).
- Clean and rinse the exterior of the sprayers (Engenia); dispose of rinsate as specified by laws and regulations (XtendiMax and FeXapan).
- Dispose of all rinsate in compliance with requirements (Engenia); drain sump, filter and lines (XtendiMax and FeXapan).
- Rinse the complete spraying system with clean water (XtendiMax and FeXapan).
By Rhonda Brooks
States Have the Final Say on Dicamba Use
Several states have the green light from EPA to use new dicamba formulations. Note however, some states, such as the following, are issuing more restrictive guidelines and laws for dicamba use.
Arkansas is limiting in-season dicamba applications between April 15 and Sept. 15 to
Engenia only. “The ban includes the use of all older dicamba formulations as well,” says Bob Scott, University of Arkansas Extension weed scientist. “We want people to understand what they’re getting into with these [new] products,” he adds. “Don’t get caught up in the hype of this technology. There are benefits and drawbacks.”
Indiana’s Pesticide Review Board wants to adopt a restricted-use pesticide (RUP) classification rule for all products containing at least 6.5% dicamba, so only certified applicators would be able to purchase and spray them, says Dave Scott, pesticide administrator for the Office of Indiana State Chemist. If passed, the Indiana rule would restrict the sale and distribution of existing and new formulations of dicamba to registered RUP dealers. However, given the timing, the rule won’t be approved in time for this coming season, he notes.
Missouri farmer and state Rep. Don Rone, R-Portageville, is proposing three bills he hopes will help prevent problems like those that occurred in the Bootheel region this past summer. One of the bills, H.R. 662, would increase the current fine for off-label dicamba applications from $1,000 per field to $1,000 per acre.
North Carolina has approved special local need (SLN) labels. SLNs differ from the federal supplemental dicamba labels EPA approved for the new formulations in two ways, says Alan York, North Carolina State University Extension weed specialist emeritus. First, maximum wind speed at application is limited to 10 mph in all scenarios. Second, SLNs require mandatory training for people responsible for applications. There are 38 training sessions underway across the state.