March 15, 2022
Given the slightest opportunity, weeds will find a way to adapt and take root in your field. It doesn’t take many escapes to cause a big problem, particularly in cotton. In the worst-case scenarios, fields may become impossible to harvest.
Gregg Gerber, Wilbur-Ellis Agribusiness sales representative and agronomist, recommends considering your target weeds and current resistance concerns to plan for 2022 and beyond.
“A lot of our chemistries provide good control,” Gerber said. “But if you control 90% of a weed population out of 10 billion, you still have an issue.”
Kochia is the first problematic weed to emerge, followed by native grasses, Russian thistle, tumbleweed and marestail. Later in the season, Palmer amaranth and morning glory pose a challenge to even the most diligent growers.
How can you manage herbicide resistance and get better control of weeds?
Make a plan. To start, look back at last season. Pay attention to what weeds were present and where escapes happened and use this information to plan your herbicide program. Continue to scout fields in-season and be ready to shift gears on chemistry if the level of control is lacking.
Residual. Residual. Residual. Yes, you probably need three residual herbicides. Determine which herbicides are the best fit for your program and layer overlapping residuals.
“A lot of times I only see two residual herbicides applied, which is a red flag,” said Nathan Foster, Wilbur-Ellis sales representative and agronomist. “We're going to get to where we need a minimum of four residual herbicides. For best results, I'd like to see five.”
Timing is everything. Don’t wait until you see weeds to apply herbicide — plan ahead for scheduled applications. Weeds are easiest to control before they emerge. After emergence, target weeds at three inches or less.
Volume. Apply herbicide at the top labeled rate for target weeds. Adequate volume is critical to get the right coverage, particularly for contact herbicides, and will help prevent economically devastating herbicide resistance.
Rotate chemistry and crop. Rotate herbicide mode of action, including residuals. If you’re observing resistance in cotton, plant corn or sorghum so you can apply other chemistries.
“Glyphosate, glufosinate and dicamba are the most used chemistries around,” Gerber said. “If we have resistance to them all, then we're going to have to manage our chemistry better and maybe adopt older practices to control weeds.”
Consider tillage. Manually uprooting weeds and moving seed below the germination zone is a tried-and-true method. However, between the cost of labor and equipment as well as the impacts on soil health and water holding capacity, it’s a balancing act for each farm.
Get equipped. Hooded sprayers are making a resurgence because they provide more herbicide options to include in your rotation. Also, be sure to use the right nozzle for the job. An air induction nozzle is needed for dicamba applications, but early season herbicides get better coverage using a flat fan nozzle with a smaller droplet size.
Extend residual control. A soil retention adjuvant such as EFFICAX® can prevent leaching and keep residual herbicide near the top of the soil in the weed germination zone. Economical and an excellent tank-mix partner, it’s an easy addition to your herbicide program.
Both Gerber and Foster agree — being proactive and exploring new (or old) solutions is the best way to manage weeds.
“We can't keep doing what we have been doing; we’ve got to think outside the box,” Foster said. "What have we not been doing that is an option? Let’s really explore those routes.”
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