Editor's Note: Dicamba herbicide use on soybeans and cotton is expected to expand dramatically in 2017. Stewardship will be critical to avoid drift and other movement onto sensitive crops and plants. This Dicamba Decisions series examines important application issues and the tough new federal label requirements of the new dicamba herbicides.
PLATTSBURG, Mo. (DTN) -- Dicamba herbicides don't leave much room for error. Damage from that chemical "shows up at much lower levels" than some other herbicides, said Fred Whitford, a professor in Purdue University's pesticide program.
That means thoroughly cleaning your spray equipment before filling it with a different compound is going to be more important than ever this year, as newly labeled dicamba herbicides come online. Doing otherwise will risk crop damage and legal ramifications, experts warn.
The burden of tank cleanout may weigh heaviest on custom applicators because of the number of acres they treat and the speed with which they must move in season.
However, with a careful job of sprayer cleanout between compounds, dicamba damage can be controlled or eliminated, Whitford said. "Listen to what the [chemical] manufacturers say," added Jacob Bolson, John Deere's application equipment aftermarket manager. "What is on the label is the law."
THREE TIMES IS THE CHARM
The XtendiMax and Engenia labels call for variations of the tried-and-true triple-rinse method to clean sprayers.
The first step is completely draining the system as quickly as possible after spraying. Research by University of Missouri weed scientist Kevin Bradley has shown that leaving just 1 to 2 gallons of dicamba spray solution in a 1,200-gallon tank can result in significant yield loss if the next application is done in a non-dicamba-tolerant field.
Both labels warn against letting the sprayer sit overnight before beginning the cleanout process. Dicamba can settle and dry into porous hose surfaces and other hard-to-reach areas. Cleanout of dried compounds is much more difficult than compounds that are still in liquid form.
In the first flush, clean water is the only required ingredient. "We recommend trying to fill the tank about half full" for all water rinses, said Ryan Rector, Monsanto technology development manager for dicamba. "The more water you use, the better off you will be."
For both XtendiMax and Engenia, the second rinse cycle includes a commercial cleaning agent -- don't rely on simple ammonia as some farmers and applicators now do.
Commercial cleaning agents come in a lot of formulations, none of which are designed mainly for dicamba.
"We don't have specific product recommendations for detergent cleaners, but whatever detergent is used should remove all sediments that Engenia might bind to," said BASF technical marketing manager Chad Asmus.
Both labels recommend circulating the cleaning agent for "at least 15 minutes."
Don't skip the third rinse with clean water. Bradley's dicamba rinse experiments still showed significant yield loss when sensitive fields were sprayed after just two rinses.
"We've done extensive in-field demonstrations and trials ... if this triple-rinse procedure is followed, they [growers] will not have spray tank contamination issues," Asmus said.
Disposing of the rinsate can be tricky, because it will contain some amount of herbicide.
Bob Wolf, an expert in agricultural spraying techniques and owner of Wolf Consulting & Research LLC, recommends spraying the first rinsate on dicamba-tolerant soybeans or in other "safe" areas. If you do spray rinsate on soybeans that have already been treated, be sure not to exceed the label rate, he said. Do not spray rinsate on buffer areas; by definition, those areas must not be treated with dicamba.
Remember to check and follow all local, state and federal laws about rinsate disposal, Wolf added.
For more guidance on how to dispose of rinsate safely, see this guide from Purdue University: http://bit.ly/….
STRAINERS AND SCREENS
"There are all kinds of nooks and crannies and hiding places, not only for the active ingredient but also for sediment and residue which the active ingredient can bind to," Asmus warned. Among the chief offenders are strainers, screens and end caps.
Older sprayers have screens at each nozzle body. Newer sprayers have inline screens that filter liquids at various places on the boom. In either case, these must be removed and cleaned, typically in a bucket with cleaning liquid. If you plan ahead and purchase a second set of screens, you can remove the old ones, replace with the new ones to save time and clean the dirty screens later.
Strainers also must be removed and cleaned during the process. End caps -- those areas at the end of booms and in other plumbing dead ends -- may be the number-one culprit in sprayer contamination, Whitford said: "A lot of crud is left over in them. It is critical that they come out for dicamba or any other product."
Sprayer manufacturers are well aware of the problem and newer models include aspirated and easily removed end caps, said Mark Burns, Case IH marketing manager. Newer Patriot sprayers have features to make cleanout quick, easier and more effective. For instance, they now have ports at the bottom of the spray bar for better cleanout.
Optional factory-installed or aftermarket end caps that fit most sprayers have features that make cleanout easier, too.
Most sprayers come with onboard air compressors for suspension systems and/or foam marker set-ups. Newer sprayers allow the compressors to do extra duty by running an air line to the booms. Forced air can aid in cleanout.
To reduce the surfaces exposed to chemicals, manufacturers offer direct-injection systems. They limit chemicals to materials tanks and the boom, where product is injected into water as it enters the boom area. That means you don't have to clean a large tank full of a chemical-water mixture. But direction injection "is not a cure-all; it's not a silver bullet," Burns said. Much cleaning remains to be done.
The ultimate machinery cleanout technology might be automated systems that allow the operator to sit in a cab and push a button. The system does much of the triple-rinse work from there. John Deere offers the Solution Command System on some of its R Series sprayers.
THINK OUTSIDE THE SPRAYER
"Think about the outside of the sprayer, too," said Rector. "Hoses, tires, other pieces of equipment can attract dust and spray residue and be transferred from one field to the next." Wash off the machine when possible.
External parts also come into play. Quick-fill hoses must be cleaned, too, if they are used to put chemical into the spray tank.
Finally, remember that spraying is a process that does not start and end in the field. That's especially true if you use a "hot load" system of mixing chemicals at the farm or shop and transporting it to the field. Tenders, hoses and other equipment could be contaminated if you used them to handle dicamba. "This whole cleanout process must go all the way back to the beginning," Wolf said.
The process is going to require patience, especially from custom applicators. "Don't cut corners," Whitford said. "Take the time to do it right."
Jim Patrico can be reached at firstname.lastname@example.org
Emily Unglesbee can be reached at Emily.email@example.com
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