Dicamba drifting to other fields seems to be the talk of the farming community as of late, but the idea of this happening is nothing new.
In fact, it was determined back in 1967 that soybeans were sensitive to the broad-spectrum herbicide.
“It is not something we haven’t seen before,” said Dr. Aaron Hager, a weed scientist from the University of Illinois.
Illinois is now number three in the United States for the number of complaints associated with dicamba application. Hager worries about dicamba being one of the only things used to kill herbicide-resistant weeds in fields.
“If that’s our solution folks, I’ll give it three years,” Hager explained at the Brandt Consolidated Agronomy Day near Lexington this week.
An absence of symptoms does not mean an absence of drift, according to Hager. Trees were killed in Tennessee with the formulation and common problems include spray tank contamination and volatilization. Growers are urged to confront neighbors if they observe them doing something wrong.
“We are one 60 Minutes newscast away from having a public relations nightmare,” Hager added.
Hager has no idea what the future holds, but predicts some changes down the road, such as dicamba only being used as a pre-planting application. Several universities are currently looking at the volatilities of these chemical formulations.
Much of Hager’s discussion also focused on weeds, such as marestail, water hemp and Palmer amaranth. With marestail, there is some good news in the fact that we typically do not see a large buildup of seeds in the soil. Also, it does not take long to get populations under control. Most marestail is now glyphosate resistant, but fall applications seem to work effectively. Burndown mixtures with three or four combinations are ideal.
“Don’t rely on just the glyphosate,” Hager cautions.
Hager urges growers to remain vigilant for Palmer amaranth, as populations of the weed can build up very rapidly if the problem is not taken care of. He refers to Palmer as a “beast” and a “water hemp plant on steroids.” There have been issues with seed mixes used for pollinator plots being contaminated with Palmer seed. If you identify the plant in a field, do whatever you can to get rid of it and assume there are more weeds if you only notice one.
“This thing is nasty. It’s not like any other species we’ve had to deal with,” said Hager.
Water hemp continues to be the number one problematic species in the state and is not going to slow down anytime soon. Hager believes we are stuck with weed resistance.
“What you’ve got to work with now is what you have to work with in the future.”
A much more integrated pest management method is required to properly manage water hemp. This includes the right rate, product and timing. Plus, a timely post application is critical and layering residuals in with the post product is not a bad idea. The key to successfully handling the weed long-term is to attack it at the most vulnerable stage of the life cycle, which is the seed.
Water hemp can germinate at soil temperatures in which many other species cannot. Hager noted one instance where a water hemp plant survived a strong rate of dicamba, which means dicamba resistance is not unheard of.