Farmers face a variety of difficult challenges as they prepare for the 2022 growing season. Shortages of herbicide products – and record high prices for what is available – plus the ever-present prospect of off-target dicamba movement are among those that vex Kevin Bradley, Extension weed specialist at the University of Missouri.
These are his top topics to watch in 2022.
1. Herbicide Shortages/Supply chain Issues
“Much has been said and written about the potential shortages of glyphosate and glufosinate that are expected in 2022. After talking about this with growers and retailers around the state and after my (admittedly abbreviated) winter meeting season, I’m also not sure who will have a shortage of these herbicides in 2022, and who won’t,” says Bradley. “I’ve heard everything from, ‘we don’t have any problem getting glyphosate/glufosinate in this area’ to ‘we will be very limited in this area’.”
Kevin Bradley
Growers who don’t anticipate being able to source enough glyphosate/glufosinate in 2022 are advised not to use them.
“Target your worst weeds with the herbicides that give you the best opportunity for success first and take every opportunity to make the most out of the herbicide that you intend to spray.” Bradley advises. Proper timing of herbicide sprays will be crucial this year (to avoid any re-sprays). Use the right nozzles, adjuvants and gallons per annum, as well as other best management practices.
“In corn, we still have a variety of effective post-emergence weed management options and herbicide groups that do not involve glyphosate or glufosinate. These would be the group 4 (2.4-D), dicamba, etc.), group 27 (Callisto, Impact, Laudis, Shieldex, etc.), and group 2 (Resolve, Steadfast, etc.) herbicides,” Bradley continues. “In other words, you can probably get by easiest in corn without glyphosate or glufosinate.”
Effective residual herbicides must be used pre- and/or post-emergence for soybeans. Farmers should have learned from the Palmer amaranth problems and waterhemp.
“Also because of our problems with these resistant weed species, soybean is a crop where a potential shortage of glufosinate might hurt the most. If used correctly, glufosinate is still an herbicide that works on the pigweed species in most Missouri soybean fields,” Bradley says.
He recommends that glufosinate is saved for post-emergence use with Enlist soybean (preferably Enlist One), Liberty Link, Liberty Link GT27 or XtendFlex soybean.
Cover crop termination is most often achieved with glyphosate, or glyphosate/glyphosate combination. These are the most reliable and consistent options.
“If I had to ‘save’ glyphosate for use this season, I’d want to try to keep some of it for cover crop termination,” he says. “But if you cannot find glyphosate and have to switch to another non-selective herbicide, our data indicates that tank mixes that include paraquat (Gramoxone) may be the next best alternative.” Another option for the control of grass cover crops would be the application of a group 1 herbicide like clethodim (Select Max, Arrow, etc.) These herbicides will not control broadleaf or legume weed species, however they can be used to control them.
2. Dicamba movement off target
“As much as I wish it weren’t the case, unfortunately the issues with off-target movement of dicamba have not ended and each season we have continued to see dicamba move off-target and injure neighboring soybean fields and other sensitive plant species,” Bradley says.
Research by Mizzou has shown that secondary movement can occur after the sprayer has left a field. This secondary movement is beyond the control of an applicator.
Growers who are planning to plant XtendFlex soy beans and spray one the approved dicamba products this year should be aware of the label requirements and the expected environmental conditions before and after application. Post-emergence applications of glufosinate can be used in XtendFlex soybean if conditions are not ideal for dicamba application.
3. Too much reliance upon herbicides
Bradley states that herbicide resistance is still a major problem for farmers. Waterhemp, for example, is now resistant to seven different herbicide sites of action groups (2–4, 5, 9, 14, 15 and 27). Palmer amaranth has nine resistances (2, 3, 4, 9, 10, 14, 15, 27,).
Bradley points out that Larry Steckel, a Tennessee specialist in weeds, and Aaron Hager from the University of Illinois confirmed the presence of dicamba resistant waterhemp populations within their respective states.
“I’m not aware of any official dicamba-resistant populations in Missouri, but we have observed a high degree of variability in the control of Missouri waterhemp populations with this herbicide in our screening efforts over the past several seasons,” he says. “All of this is just simply to say, our growers as well as our entire industry needs to be more open to an integrated approach to weed management that considers all available options, not just herbicides.”
The treadmill approach to weed management with herbicides, where the industry promotes one mode of action until it breaks, and then switch to another until that one breaks, and so on, isn’t sustainable.
“We must start including other preventative, cultural and/or mechanical weed management practices into our programs before it’s too late,” he says.
Source: Successful Farming
