Adjuvants Trending Up For Fighting Weed Resistance
Gone with the wind are the days when adding an adjuvant to the spray tank was looked at with major scrutiny. With crop protection chemistries becoming more expensive by the day, and the industry ready to embrace new chemistries that require a higher level of management (compared with glyphosate and the like), making sure herbicide molecules make it to their destination weed unencumbered is a top priority for those on the front lines of America’s war against resistant weeds.
United Suppliers (U.S.) is just one of many companies supplying those applicators, and Dr. Patrick McMullan, adjuvant development manager, says that overall the industry is trending toward using more combinations of different adjuvants in a system, as opposed to simply throwing a surfactant and ammonium sulfate in the tank and calling it a day.
“We’re seeing more oil-based adjuvants like Methylated Seed Oils (MSO) and crop oil concentrates, and more ammonium sulfate in the tanks lately,” admits McMullan. “We’re also seeing a lot of combinations of stuff like ammonium sulfate added with a Drift Reduction Technology (DRT) and a surfactant.”
McMullan says things are changing rapidly though from the days of glyphosate, when all one needed was some ammonium sulfate plus a water softener and maybe a little bit of surfactant in there.
He also says the Ames, IA-based company is keeping busy with its development efforts of adjuvants and adjuvant combinations for the new Enlist Duo herbicide (2,4-D), as well as BASF’s Engenia and Monsanto’s XtendiMax (dicamba).
“There’s some new restrictions with those systems, dicamba for instance cannot be mixed with any ammonium containing product because it becomes more susceptible to volatilization,” he explains. “Generally speaking we are looking at some new molecules for enhancing herbicide uptake into the weed as well as new water conditioners since ammonium is restricted with that chemistry.”
McMullan says the company has received good guidance from Dow, BASF and Monsanto on developing adjuvants for the new herbicide systems, but US is still awaiting word on what the protocol will be for label approval of new adjuvants.
“EPA controls the label, so this is just our best guess but we believe EPA will end up being the ultimate authority on approvals, with guidance from the chemical companies so we’re not putting anything into the tank that effects efficacy negatively.”
Coming down the pipeline in the next couple years is a new “standalone DRT” product that McMullan claims “would be quite unique in the market” and some new surfactants that could have a “real strong fit” in the market. He also says the company is reevaluating its adjuvant portfolio, so there’s a possibility U.S.’ adjuvant offerings could look completely different in 5 to 10 years than it does today.”
Specialty products manufacturer Atlantic-Pacific Agricultural’s (APA) Joe Brennan, product development manager, agrees that adjuvants with a multi-faceted fit in cropping systems are “the thing now, but Hook has been the thing for years. It does everything: wetting, spreading, sticking, activation, canopy penetration, as well as drift control (spray deposition).”
Hook is Englewood, FL-based APA’s flagship adjuvant product and has been around for “over 20 years”, according to Brennan. He says that Hook is used extensively in potatoes with paraquat applications, as well as in herbicide applications in soybeans to control resistant marestail and waterhemp.
“Those two key weeds in soybeans are problematic, especially with plants that emerge in May and June, that time of year you don’t want to go slapping a bunch of herbicides down,” says Brennan. “Glyphosate for example, you can only apply so many ounces of that per year, and if you exceed that and you still have weeds then there’s many different herbicides you can add to the tank mix.”
Another area that Hook is deployed is in situations where volunteer weeds remain throughout the season despite initial applications.
“You get the volunteer weeds; the corn in the soybean patch and the beans in the corn field,” explains Brennan. “There’s a lot of volunteer herbicides that you can go back in the field with, and adding an adjuvant with multi-functional properties you most assuredly get those weeds eradicated.
Hook is labeled for both ground and aerial applications, and Brennan wanted to stress that it is also used in mid-season insecticide and fungicide applications (as well as in weed-and-feed systems).
“Throughout the season guys can have issues with rain events washing off inputs and you have to go back and reapply, you’ve got to have an adjuvant in there.”