Know the equipment, the products to use and your field conditions before heading out
There are multiple new crop protection formulations and combinations on the market this year that make following the label, knowing your field conditions and prepping your spray equipment even more important.
“There is not a simple, one-size-fits-all formula,” says Mark Mohr, tactical marketing manager for AGCO. “Follow general guidelines, but certainly do whatever the label says for a particular product.”
For some products, this will likely mean the use of a specific brand and type of spray nozzle to work with a specific formulation. For instance, when using XtendiMax herbicide with VaporGrip Technology on dicamba-resistant soybeans this year, one of the only nozzles approved for the job is a TeeJet TTI11004. Note that for this product and nozzle, the maximum pressure is 63 psi with a minimum spray volume of 10 gallons per acre applied at a maximum ground speed of 15 mph, with the spray boom no more than 24 inches above the target.
“The label tells us the right nozzle to use at the right pressure to get the right droplet size—big enough to stay on the target area and deposit on the intended plants,” says Mohr.
Also, the air induction nozzles approved for use with the new dicamba formulations are not compatible with aftermarket pulse width modulated (PWM) flow-control systems, which sometimes are added to sprayers. Turn off PWM so that continuous spray will be delivered from the nozzles.
ISSUE: Machine Speed
The speed of your sprayer can alter the effectiveness of your product and potentially contribute to drift. Most self-propelled sprayers won’t be run faster than 15 mph in the field, while pull-behind tractor models will generally be used at 6 to 7 mph, according to Mark Hanna, an Iowa State University Extension ag engineer.
At 15 mph or greater, according to Hanna, “edges of the fan-shaped spray pattern get distorted. The controller will also increase pressure in the boom, and that can give you smaller droplet sizes.”
The smaller droplets may not be important for some products, but for others it may prevent the treatment from “moving down into the crop,” says Hanna. Such small sizes are also more prone to drift and contamination of non-target crops, especially with the new dicamba formulations.
ISSUE: Wind Speed
It is possible for safe spraying to occur under some circumstances when wind speeds are above 10 mph, but the liability risk of drift would caution against this, according to AGCO’s Mohr.
“Any wind speed specified on the label must be followed,” he says. However, some labels don’t specify a wind speed; they merely offer the admonition to “avoid drift.” That type of label requires the applicator to “understand how to manage drift and understand the consequences under state law, label enforcement actions and liability,” says Mohr.
ISSUE: Boom Height
The drift issue in general is causing people to think more about things like boom height management, according to Mohr. Automated boom height systems with ultrasonic sensors keep the boom at a consistent height above the canopy.
“Those systems are oftentimes looked at as just operator convenience tools so the farmer gets less fatigued,” says Mohr. “But they help prevent boom height from becoming too low and causing skips or too high and exposing the spray to drift.”
Hanna agrees that boom height is critical. “Two new dicamba products recently labeled specify a maximum of 24 inches above plant height,” he says.
“Most people will be using nozzles that have 80-degree to 110-degree flat fan orientation,” says Hanna. “Doubling the boom height from 20 to 40 inches will allow the lateral trajectory of small droplets moving off-target to basically double the off-site distance they move.” Hanna says it isn’t unusual to see self-propelled sprayers in mid to late June with booms 3 to 4 feet above the crop surface. “Get those booms down a bit,” he says.
After a job, “every square inch of plumbing is cleaned out, and multiple times,” says Mohr. Cleaning should include not only the spray booms and tanks, but also bypass lines and sprayer screens, using water and cleaning agent.
Hanna urges producers to make sure they clean the top of the inside of the tank, which can be overlooked. Additionally, some growers and commercial applicators use multiple outlet nozzle bodies on their booms. These bodies, or turrets, often accommodate three or five separate nozzles on a rotating turret that can speed the changeover from one spray formulation to another. As spray formulations continue to specify particular nozzles or groups of nozzles, the likelihood these turrets will get more use increases. “Use of a turret complicates sanitation and clean-out, as nozzles and screens should all be removed and cleaned separately during flush and cleaning cycles,” says Hanna.
The new dicamba labels are the current “poster children” for specific nozzles, he adds. “But Enlist Duo® label is also very specific over a range of nozzle types and operating pressures. I know we say it 800 times, but the label is the law.”