USA - How to navigate herbicide shortages

By Gil Gullickson

Good news exists for soybean farmers.

Although total exports for 2021-2022 haven’t matched those of 2020-2021, they’re still healthy and should drive strong prices for 2022.

“You have to go back to 2016 and 2017 to find a year that’s even comparable with 2020-2021 exports,” says Bryon Parman, North Dakota State University Extension agricultural economist.

There’s a flip side, though, to strong prices.

Higher commodity prices don’t necessarily mean higher net profits,” says Brad Doyle, the American Soybean Association president who farms near Weiner, Arkansas.

“With all this technology we have available, we are reducing our environmental footprint by using equipment that cuts out overlaps with spraying and fertilizing. We’re doing the right thing and our yields are increasing, but this technology costs money,” he says.

Fortunately, soybeans aren’t as dependent on fertilizer as corn, because they fix their own nitrogen.

HERBICIDE SHORTAGES

Still, challenges exist, such as 2021 herbicide shortages, that will continue this year.

“I’ve been in this position for 18 years, and I’ve seen herbicide shortage discussions come and go,” says Kevin Bradley, University of Missouri Extension weed specialist. “Never has it been more clear that this is the real deal. We’re talking about major products like glyphosate [Group 9] and glufosinate [Group 10] and even 2,4-D [Group 4]. Those are three of the top four most common postemergence-applied soybean herbicides.”Glufosinate (Liberty) supplies are particularly suspect. Although legal to use in the United States, over 30 countries have banned the nonselective herbicide paraquat.

“What is an alternative to paraquat?” asks Rodrigo Werle, University of Wisconsin (UW) Extension weed specialist. “It’s glufosinate.”

Further squelching glufosinate supplies is an anticipated increase in use by U.S. farmers who will plant XtendFlex soybeans that feature tolerance to glyphosate, glufosinate, and dicamba (Group 4).

Farmers who planted XtendFlex soybeans in 2021 may rotate from dicamba in 2021 to glufosinate in 2022, Werle adds.

Shortages are also spiking chemical prices, he says.

Expect more generic product shortages compared with branded products. Many herbicide components in generic components are manufactured in China, which has slowed production. Meanwhile, COVID-19 still looms, and could shut down plants making all kinds of agricultural chemicals, he adds.

WHAT TO DO?

Farmers who haven’t done so should line up chemicals now.

“Many retailers are saying if you we get to June and July and they’re out, you [farmers] are out,” says Bradley.

Be flexible. For example, farmers who cannot access glufosinate to apply with 2,4-D choline on Enlist E3 soybeans may instead opt to use a grass herbicide such as clethodim (Select, Group 1) instead if it’s available, says Bradley.

“None of us likes such a scenario, but we may be forced into it,” he adds. Think back to last year when planning this year’s chemical program, advises Andy Carriger, a Corteva Enlist technology specialist. “Make a judgment based on what kind of weed problems were in a field,” he says. “You can look at tillage or a revised preemergence program or a trait that matches the weed problem.”

In many cases, the problem weed has been and still remains waterhemp.

“It is a highly adaptive weed,” says Matt Montgomery, a Pioneer field agronomist. “It has male and female plants and can even hybridize. For now and in the foreseeable future, it will remain the driver weed in the Midwest.”

Kelly Garrett concurs. “I had late waterhemp escapes last year,” says the Arion, Iowa, farmer. “With the dry weather, not a lot of chemistries worked as well as they did in the past.”

Waterhemp isn’t the only weed in town. Garrett has revamped his weed management for 2022, incorporating a fall herbicide program to control winter annuals, such as marestail, with plans to beef up spring preemergence programs.

The inability to secure glyphosate and also clethodim for 2022 could aggravate grass and volunteer corn control, says Werle.

Although broadleaves such as waterhemp now resist glyphosate, it still controls grasses and several other broadleaf species well.

“We don’t realize how important glyphosate is until we don’t have it,” says Werle. “We have chemical programs that are pretty good on waterhemp and other small-seeded weed species, but not necessarily so on grasses and large-seeded weed species.”

That’s why farmers need to be prepared to fine-tune programs to manage grasses and large-seeded broadleaves (such as cocklebur and giant ragweed), he adds.

SEEDBANK MANAGEMENT

Nixing weeds from going to seed is also key. Werle fielded questions last year regarding why Wisconsin velvetleaf infestations occurred after a nearly 10-year absence.

“It was a dry year [in Wisconsin], and velvetleaf thrives in dry years,” he says. Even after 17 years, 25% of velvetleaf seed may still survive in the soil, according to University of Nebraska research.

“If you let it go to seed for one year, you will be dealing with weeds like velvetleaf for years to come,” Werle adds.

Enter cover crops.

Green planting soybeans into standing cereal rye can squelch sunlight and thus weed emergence.

In 2021 UW trials, biomass equivalents of 6,000 pounds per acre of cereal rye suppressed weed emergence by 50%, he says. Even only 1,000 pounds per acre of cereal rye biomass suppressed waterhemp growth by 50%.

“Reduced amounts of cereal rye biomass do not necessarily reduce the amount of waterhemp that emerges, but it slows growth,” says Werle. Consequently, this can reduce pressure on postemergence herbicides to control weeds, he adds.

“A cover crop is not a silver bullet,” adds Bradley. “It will not provide season-long weed control of weeds like waterhemp. What it can do is prevent or delay the emergence of waterhemp, which in most cases it does.”

SYMPTOM, NOT THE PROBLEM

Dicamba damage symptoms that once again surfaced in 2021 are just part of a bigger picture that revolves around herbicide resistance, says Joshua Stamper, director of the Minnesota Department of Agriculture’s pesticide and fertilizer management division.

“When you see news articles about antibiotic resistance and you replace the word antibiotic with pesticide, it’s the exact same article,” he says.

University weed scientists already confirmed waterhemp populations in 2021 that resist dicamba in Tennessee and Illinois. That’s why rotating herbicide sites of action and layering preemergence residual herbicides are key for not only effective control, but also for forestalling resistance, Stamper says.

“The challenges that we have with dicamba damage are, more than anything, a reflection of the fact that we are losing [effective] chemistry at a rate that is unsustainable,” he says.