Chemical selection, proper technique important in bare ground weed control
According to Scott Votaw, owner of Field Services and Weed Control in Cody, several components must be considered to be successful in bare ground weed control programs.
He defined bare ground weed control, saying “We want treated areas to be vegetation free for an entire year. When I say vegetation free, that means nothing.”
The top priority for bare ground weed control is selecting the correct herbicide, said Votaw.
“Questions we need to ask include, what are the main weeds? Are they grasses, annuals or perennials?” he continued. “All of those are going to require a little something different to control them.”
Illustrating with a fateful story, Votaw stressed that it is important to consider non-target species that are in the area when selecting a chemical.
“What’s going to happen is, many of these things are water soluble, so when it rains, the chemical will go somewhere else we didn’t intend for it to go,” he commented. “I had a guy who sprayed the parking lot at the fairgrounds. At the bottom of the parking lot along the ball fields, they had a whole row of ‘In Memory Of’ rosebushes that are no longer there as a result.”
Proper agitation technique is important for bare ground weed control.
“Most people don’t have the correct equipment. It can get clogged up in the bottom of the tank, or we get it to spray but none of the herbicide comes out because it was all in the bottom,” said Votaw. “We want to make sure that we have constant agitation.”
According to Votaw, adequate coverage is another important factor that applicators should pay attention to.
“We need to get the area covered with a nice, even coverage,” he continued. “If we put out 100 gallons of water to the acre, and we put 90 over there and 10 on the rest of it, that’s not good coverage.”
Droplet size and spread is important for controlling product drift, and Votaw advises that applicators use low-drift nozzles and dye.
“It’s a heck of a lot cheaper to put in dye and know where we’ve been than have to come back later or overlap too much,” he commented.
“Resistance is naturally occurring heritable traits that will survive a herbicide treatment that would naturally kill it,” said Votaw. “Resistance is absolute, no matter how much we put on.”
Votaw explained that there are multiple types of resistance, including cross resistance and multiple resistance.
“Multiple resistance is defined as resistance to more than one mode of action,” he noted. “That’s where we get into a lot of problems.”
Plants are able to develop resistance through a variety of avenues, he explained.
“They can develop resistance through genetic mutation or biotypes. Inside the plant, they can have an altered target site,” continued Votaw. “With enhanced metabolism, we have a plant that can break down the herbicide a lot faster than susceptible plants.”
According to Votaw, many factors can contribute to growing herbicide resistance.
“Some factors that lead to resistance include frequent use of herbicides with the same mode of action, not using any other measure and monoculture cropping systems,” he continued.
Votaw advised, “We need to rotate our herbicides and avoid using the same thing over and over. Limit the application of single herbicide. When possible, we should use tank mixes or sequential applications with different modes of action.”
Votaw noted that it is important to monitor the results of herbicide treatments.
“Typically if it doesn’t work, the customer will call and let us know,” he said.
While failures can occur for other reasons, most treatment failure is due to applicator error.
“It’s almost always the applicator. Almost 75 to 80 percent of the time, it’s applicator error. The rest can be grouped into environmental,” commented Votaw.
It is imperative to be thorough and use the most effective treatment, said Votaw.
“Do it right the first time. The $50 program is not always that cheap if we have to go back and re-treat,” he concluded. “Don’t always use the lowest herbicide rates. That encourages resistance, and if conditions are not ideal, we will have breaks.”
Votaw spoke during the 2016 Wyoming Weed and Pest Council Conference.
Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.