New herbicide tolerant crop technologies, intended to help fight growing problems with herbicide resistant weeds, are also adding to the complexity of managing potential spray drift, a challenge that became evident last year when thousands of acres of crops in the lower Midwest were injured, resulting in strained relationships and, in one case, a highly publicized murder.

New herbicide tolerant crop technologies, intended to help fight growing problems with herbicide resistant weeds, are also adding to the complexity of managing potential spray drift, a challenge that became evident last year when thousands of acres of crops in the lower Midwest were injured, resulting in strained relationships and, in one case, a highly publicized murder.

“When you start influencing what producers can and can’t do with their property, or messing with their livelihood, it creates a touchy situation,” said Josh Bushong, northwest area agronomist for Oklahoma State University.

In an effort to be proactive, OSU’s agronomy department launched a series of educational meetings this spring.

“Soybeans are extremely sensitive to dicamba, and cotton to 2,4D, and it doesn’t take a lot of drift to start getting issues on these crops,” said Todd Baughman, an OSU weed scientist. “We want to be sure we don’t get into the same situation some of these other states have gotten into.”

Over-the-top herbicide treatment of crops, which began with the introduction of Roundup-ready technology in the late 1990s, caught on quickly with farmers. Now, as more glyphosate resistant weeds appear, chemical companies are “stacking” glyphosate resistance with resistance to other herbicide chemistries within the same plant.

More specifically, glyphosate resistant soybeans, cotton and corn are now being engineered with resistance to 2,4-D (Dow’s Enlist technology) or with resistance to dicamba (Monsanto’s Xtend line.)

Coupled with increasing crop rotation and diversification across the High Plains, that makes communication, documentation and overall herbicide management increasingly important, noted Heath Sanders, OSU’s southwest area agronomist, who added that economics are dictating farmers will plant more cotton and soybeans than in previous years.

“We could see a lot of double-crop soybeans this year, and they could all potentially have resistance to different chemistries,” he said.

Bushong noted last year’s drift problems largely caught the industry by surprise.

Up to as many as 200,000 acres of crops were injured in Missouri, Arkansas and Tennessee after some farmers planted the new crop technologies but used old versions of herbicides instead of new formulations still awaiting label approval by the Environmental Protection Agency. In one case, a confrontation between two men on an isolated country road resulted in a scuffle that led to a shooting death.

The potential for herbicide drift is nothing new. In fact, the introduction of 2,4-D resistant cotton could help boost acreage in southwest Kansas, Bushong said, because many farmers there have been afraid to plant it next to pastures for fear the popular herbicide would drift onto their land.

The new herbicide formulations are designed to be less volatile, and while they do represent clear advances in technology, applicators and farmers shouldn’t be lulled into a false sense of security, Baughman said.

“I’ve walked lots of drift issues,” he noted. “I would say 95 percent of drift issues are wind-blown drift, and only about 5 percent are related to volatility.”

Commercial applicators, which are subject to oversight by state and federal agencies, should expect regulators to be on high alert this season, he added. “With the issues we’ve seen in surrounding states, my guess is they are going to be on top of it pretty close,” he said. “Fortunately we didn’t see what some other states did, but that information’s out there and these guys know about it and they will try to be a little more proactive.”

Applicators can be fined, or, in extreme cases, sued for damages, Baughman said.

Anyone making herbicide applications should prepare to invest some time studying all relevant labels, which spell out legal use of the product, he said. That includes allowable tank mixes, recommended spray nozzles and boom heights, and in some cases adjuvants or other additives, and proper buffer distances from sensitive areas.

Detailed instructions are also provided for cleaning out sprayer systems, which typically consists of a triple-rinse process sometimes combined with use of a cleaning solution.

Chemical companies are becoming much more specific about which spray nozzles and settings to use, explained John Long, an OSU bio-systems and engineering specialist.

“This is new,” he said. “There are lots of nozzles on the market, but for the first time they are looking at specifying a brand and a model number and a size of spray nozzle you have to use for that product.”

The nozzle pressure settings are trending toward those that produce larger droplet sizes, Long said. Heavier droplets are less prone to drift but are also more widely spaced, requiring greater precision at application.

Another change the specialists noted is that companies are now requiring application at lower boom heights. Such clearance will likely be hard to maintain with today’s large 124-foot sprayer booms traveling at the speeds many applicators use.

“We won’t go smaller (with our rigs) but I’m hoping we do slow down,” Bushong said.

Also new is that these labels are considered “live,” which means the applicator must consult the product label online within two weeks of application to get the most recent updates about recommended procedures, Long said.

Chemical companies are becoming increasingly rigorous with their guidelines, but applicators too might want to think about carefully documenting their procedures, the experts said. Environmental readings should be taken and recorded at multiple points during a spray operation.

Just how critical atmospheric conditions can be was driven home by the widespread crop injuries that occurred last year.

Much of it is now being attributed to what is called a “temperature inversion,” which occurs when air becomes trapped close to the earth’s surface instead of dissipating.

In a nutshell, an utterly calm evening might turn out to be the worst time to spray.

“When we have air stability, hot air is moving up into the atmosphere, and as it’s rising, it’s cooling,” explained Misha Manuchehri, an OSU canola and small grains weed specialist who previously worked on cotton in the Texas panhandle. “When we have a temperature inversion, a layer of warm air gets trapped between two layers of cool air. That causes those droplets to linger close to the ground for a few hours up to a few days.”

Manuchehri also noted that low humidity could increase a chemical’s volatility.

“It sounds a little counterintuitive, but that plant cuticle can be hardened off because it’s a little bit stressed,” she explained. “If plants are stressed, that herbicide droplet is sitting on the leaf longer, and there’s a greater chance of it moving off-site.”

“What we want is ideal conditions for plant uptake and adsorption,” she concluded.