Taking Down Spray Drift
Applicators need to revisit basic spray practices to reduce drift, but they can also look forward to re-tooling of classic herbicides to help.
May 1, 2012
While it’s been a bane of crop protection for decades, off-target spray may finally be meeting its match. Advances in equipment, chemistry and spray techniques are coming together like never before this year, and application experts we talked with expressed a new high level of excitement about and hope for multiple strategies to deal with the problem.
First, there’s a growing movement to retrain applicators in light of increasing weed and insect challenges, including off-target spray. A key in controlling drift is using best management practices, some very elementary, some more cutting-edge, says Bob Wolf, retired application technology specialist at Kansas State University and now owner of Wolf Consulting and Research LLC, Mahomet, IL. For instance a simple part of spraying is calibration, and some applicators don’t do it, he says. Even the best brand-new units need tweaking before they actually hit the field.
Wolf is working with The Asmark Institute to conduct training schools, traveling across the country to show applicators spray techniques, including how to set up a nozzle, pressure and speed. He held meetings last fall and this spring, coaching some 400 students — some of whom attended because of drift complaints or at the suggestion of insurance companies balking at paying sometimes “astronomical” settlements in drift claims.
Training emphasizes the premise that not all chemicals require the same droplet strategy, and applicators can’t provide the best coverage with one just nozzle type and set-up. And they can’t use the latest drift reduction nozzles the same way they’ve used older technologies.
In fact, some manufacturers’ labels are starting to classify what droplet size (fine, medium, coarse) is needed for their product to do a good job. This information is “a whole new concept,” says Wolf.
“Labels are helpful, but I’m not sure how much of them get read,” he points out. “The more information that goes deeper into the label and the more material on the label, the more challenging that is,” he says. Wolf is encouraged that manufacturers will be making efforts in the future to have this kind of information online or available via phone apps. In addition, ground application equipment companies and nozzle manufacturers such as TeeJet, Hypro, Wilger, Greenleaf and CP are working on apps for phones to create more of a prescription approach, processing all the operating parameters of a spray job.
Wolf cautions that if an applicator doesn’t follow new label instructions and the product doesn’t work — causing him to call a manufacturer for support on a re-spray — that company has the right to ask critical questions to find out if the chemical was used off-label. The same scenario goes for a drift claim. State or local agencies responsible for handling claims could ask the same key questions, and if an application is off-label, the operator could be subject to penalties.
Another issue Wolf is concerned with is whether applicators can convince company leadership that practices are changing. “The applicators, especially those attending my workshops, have a more recent education about spraying than supervisors who may be making decisions for them on when to apply, where they go, and how to set their sprayers,” he says. It is important that all in the chain of command for the spray process are well-informed with this new knowledge.
Nozzles And Additives
That knowledge may call for a nozzle overhaul on sprayers, with a switch to the latest air induction/venturi nozzles, priced from $9 to $12 each. On a new sprayer with 120-foot boom and 72 nozzles on 20-inch spacings, that’s $720 for one nozzle, Wolf calculates. “I would suggest operators put a nozzle body turret that’s capable of handling three, four, or five nozzles at each location,” he says. “It’s quite possible applicators might need three or more nozzles on their sprayer during a season to meet some of these needs.”
He believes the cost should not be an issue, especially if operators are spending up to $350,000 for a sprayer. “At $720, the nozzles are incidental,” says Wolf. “It’s a different way of looking at things.”
Wolf has also done extensive work with drift control agents over the past several years. He’s found that not all are effective, and some even cause more drift when added to the tank, dramatically shifting or altering droplet size from what it should be.
Carlos Corvalan, associate professor of food science with Purdue University, reported in March that in particular, using both a surfactant and polymeric additive in a tank can lead to the formation of smaller “satellite” droplets that drift. But carefully modulating the strength, concentration, or ratio of surfactants to polymeric additives can lessen or eliminate the creation of these droplets.
Wolf is advising applicators that it could be possible to achieve the best results simply with a drift control nozzle — some of the better ones reduce driftable materials to a minimum — and there’s little to no further value in adding other compounds for drift control. In fact, adding some compounds may result in reduced coverage on the targeted pest, resulting in poorer control.
In the past, manufacturers have faced a limitation in product testing: They could only use water in spray simulations when measuring spray droplet characteristics because of safety issues, and they haven’t been able to run live chemicals in solutions in laboratory situations. But in the last two to three years have seen the development of wind tunnels with scrubbers at the end of a test line. Chemicals in a spray solution, applied at one end of a wind tunnel and measured as they pass the laser system, can be scrubbed out before becoming a hazard to technicians or the environment around the test facility.
Wolf is particularly excited about a new wind tunnel facility in North Platte, NE, formerly a swine research barn at the University of Nebraska’s West Central Research and Extension Center. The building makeover, costing nearly $1.2 million, was financed by BASF, Winfield Solutions and Wilbur-Ellis Co., as well as grants and loans through UNL’s Agricultural Research Division.
Wolf believes the facility will be busy 24/7, 365 days a year “because all the chemical companies are getting in line with this need. They want to give the best advice on these products and get that information on the label so applications can be most effective,” he says.
The only other active wind tunnels of this kind are in the United Kingdom, Australia, Canada, and at a USDA facility in College Station, TX.
New Systems Impact Drift
Drift experts we talked with agreed it’s urgent that U.S. agriculture find a way to offset the problems caused by growing numbers of herbicide-resistant and hard-to-control weeds. The crop protection industry has needed to add more active ingredients into the mix, literally, and is focusing on three chemistries a great deal: Glyphosate, 2,4-D and dicamba.
“For the last 15 years straight, glyphosate scenarios have been an ‘easy button,’ but that doesn’t work anymore,” says Wolf. “We’ve got to have combinations of products to overcome that resistance.”
Soon to market will be Dow AgroSciences’ Enlist Weed Control System. It includes Enlist Duo herbicide — a premix of glyphosate and the company’s new 2,4-D choline — and stacked traited corn, soybeans and cotton tolerant to both of these herbicides. Enlist Duo is sprayed over the top of crops.
2,4-D choline is a new form of 2,4-D never before seen in the marketplace that is a component of what Dow calls “Colex-D Technology.” Damon Palmer, U.S. commercial leader, Enlist Weed Control System, says the technology package “also includes the latest formulation science and a proprietary manufacturing process.” These advances provide ultra low volatility and minimize the potential for physical drift. In fact, Palmer says that when users couple the Colex-D technology with the right nozzle they can see a 90% reduction in spray drift.
Colex-D also promises reduced odor and better handling characteristics. “In the past, 2,4-D and glyphosate didn’t necessarily mix well together,” says Palmer. Colex-D solves this compatibility problem.
Palmer emphasizes that the Enlist system has come after years of work, including outreach to industry members across the ag value chain. “As we talked to users we realized there were attributes they absolutely loved about 2,4-D, and weed control was right at the top of the list,” he says. But some perceptions about volatility and physical drift needed to be addressed.
Dow’s research to develop the system has been in collaboration with some key universities across the country — including the University of Nebraska and Mississippi State University — as well as the University of Queensland in Australia.
As for a release timeline, the company plans to launch the system in corn for the 2013 growing year, soybeans for 2015, followed by cotton. To sustain the system, Dow is also starting Enlist Ahead, a management program that offers product use education and incentives such as discounts on spray equipment, to help retailers and growers apply with the proper equipment.
Palmer encourages Enlist Weed Control System customers to look for the best management practices that his company will be recommending because they’re heavily steeped in research. “And we’ll have a very massive training effort underway to train end users as well as the channel,” he says. “We really look to collaborate with retailers and distributors because we know they’re key in educating end users.”
Monsanto and BASF have teamed up to develop a weed control system which includes innovative dicamba formulations proprietary to BASF and the dicamba tolerant trait for soybeans (called Roundup Ready 2 Xtend), which is proprietary to Monsanto.
Set for release in 2015, the soybeans will be tolerant to dicamba and glyphosate — and the dicamba will be offered in new formulations promising minimal drift. Varieties will be a part of the Genuity Roundup Ready 2 Yield soybean platform.
This strategy will allow preplant burndown or postemergent application of glyphosate and dicamba tank mixes. The Roundup Ready Xtend Crop system will be an integral part of Monsanto’s Roundup Ready PLUS Weed Management Solutions program, designed to offer expert control recommendations plus financial incentives to growers to offset the cost of using qualifying residual herbicides.
Monsanto also has dicamba-tolerant corn, cotton, and canola in its research and development pipeline.
Word of the return to 2,4-D and dicamba chemistries is not going unnoticed by vegetable, fruit, and other specialty crop producers. These commodities are particularly sensitive to drift and volatility injury from the two active ingredients, which act as plant growth regulators. This past winter’s grower meetings have featured sessions focusing on the technology.
When Granules Take Off
Earlier this year, CropLife® magazine reported on a new granule technology that virtually eliminates spray drift. Collaborators in its development, funded in part by a $5 million grant from Ohio’s Third Frontier Program, include The Andersons, the OhioBioProducts Innovation Center (OBIC), Ohio State University’s Ohio Agriculture Research and Development Center (OARDC), Syngenta, PSB Co. and the National Lime and Stone Co.
Tim Birthisel, research and development manager with The Andersons, explains why the science behind granules makes them an especially effective weed and drift approach tool for 2,4-D, dicamba and glyphosate. For instance, with dicamba, the compound needs to be in its acid form — but this form is insoluble and doesn’t make a very good tank mix in general, he says. “In tank mix formulations, you have to do another reaction step to turn them into an ester or a salt, which is soluble. We leave them alone, they’re already in the right chemical form to kill weeds, so there’s none of this back and forth chemistry.”
Particle size is also a factor in the granules’ efficacy. EPA’s spray drift task force has found the best size for preventing drift is 141 microns, and the cooperating research team can now ensure there are no particles smaller than that in their spray (see figure). “They don’t evaporate because they’re solid, and they don’t get any smaller. We can show in a practical sense, drift elimination,” says Birthisel.
Viscosity plays a role in liquid spray mixtures, and applicators can add adjuvants to a mix so droplets won’t shatter into smaller particles. “But there’s a limit with how far you can go with viscosity when the liquid is being pushed through a tiny little hole on a spray nozzle,” he says. With granules, he says the active ingredient is delivered in a glueball that will never roll off the leaf. The glueball is formed in flight by the wetted granule applicator.
In trials last summer, collaborators pitted their dicamba foliar granule against “the best spray available, according to our weed researchers,” says Birthisel. “We significantly outperformed the spray in treating three weeds.”
The team realizes a move to granules involves a change in application habits. So far research spray work has been done with backpack and smaller-sized pneumatic granule applicators, but this summer trials begin in Ohio using an 80-foot wide boom. Birthisel believes pneumatic units will become more popular because of their precision benefits — and users will just need to hang a sprayer boom on the platform to transform it into a wettable granule applicator.
Birthisel has taken the technology to California, where specialty crops may be the first to use it on a larger scale. This spring, dozens of stakeholders there including crop consultants, research and development scientists, and weed researchers were very interested in and impressed with the approach. So far, no one company has officially signed on to take the concept to market, but the approval process is underway at EPA, and collaborators hope to go commercial in 2015.