FOCUS-Crop-killing weeds advance across US farmland as chemicals lose effectiveness

    By Rod Nickel and Tom Polansek
       WINNIPEG, Manitoba/CHICAGO, Jan 16 (Reuters) -
C rop-killing weeds such as kochia are advancing across the U.S.
northern plains and Midwest, in the latest sign that weeds are
developing resistance to chemicals faster than companies
including Bayer  and Corteva  can develop new
ones to fight them.
    In many cases weeds are developing resistance against
multiple herbicides, scientists said.
    Reuters interviewed two dozen farmers, scientists, weed
specialists and company executives and reviewed eight academic
papers published since 2021 which described how kochia,
waterhemp, giant ragweed and other weeds are squeezing out crops
in North Dakota, Iowa, Wisconsin and Minnesota as chemicals lose
their effectiveness.
        Over the last two decades, chemical companies have
reduced the share of revenue devoted to research and development
spending and are introducing fewer products, according to
AgbioInvestor, a UK-based firm that analyzes the crop protection
        Farmers say their losing battle with weeds threatens
grain and oilseed harvests at a time when growers are grappling
with inflation and extreme weather linked to climate change.
    "We're in for big problems over the next 10 years for sure,"
said Ian Heap, director of the International Survey of Herbicide
Resistant Weeds, a group of scientists in over 80 countries that
maintains a global database. "We are in for a real shake-up."  
        The database records reduced effectiveness for
glyphosate, one of the most common herbicides, against 361 weed
species, including 180 in the U.S., affecting corn, soy, sugar
beets and other crops.
    Some 21 weed species globally showed resistance to dicamba,
the most recent major U.S. chemical, which launched in 2017. 
    Environmental groups argue that farmers should embrace
natural weed-control methods instead of chemicals.
    Kochia, which spreads as many as 30,000 seeds per plant, can
cut yields by up to 70% if left unchecked, according to Take
Action, a farmer resource program of the United Soybean Board. 
    Other factors, including the development of more robust
seeds, have pushed overall global crop yields higher. But
scientists expect weed problems to worsen, with some weeds
showing resistance to chemicals even on first exposure.
        'REALLY SCARY'
    In Douglas, North Dakota, farmer Bob Finken sprayed dicamba
and glyphosate to kill late-season weeds. Neither product
eliminated kochia.
    "That was really scary," said Finken, 64. "Each year seems
to get a little worse."
    Finken was forced to clear the weeds with harvesting
equipment, which risks clogging expensive machinery.  
    Other farmers are hiring workers to pull weeds by hand, said
Sarah Lovas, an agronomist with GK Technology, a precision
agriculture firm.
    North Dakota was the largest spring wheat producing state in
2023 and ninth-biggest soybean grower.
        Five of North Dakota's 53 counties have confirmed
populations of dicamba-resistant kochia, a year after it was
first reported in the state, North Dakota State University weed
specialist Joe Ikley said.
     "It's just a matter of time before it hits your farm," said
Monte Peterson, 65, who grows soybeans near Valley City, North
    Chemical producers Bayer, Corteva and FMC  say longer
development and regulatory processes have constrained new
products to combat weed resistance. Industry executives say
regulators have become more stringent about environmental and
health impacts.
    The U.S. Environmental Protection Agency (EPA) said
standards for approving new herbicides have not substantially
changed since 1996. However, the EPA said recent efforts to
assess the impact of new active ingredients on threatened plants
and wildlife have delayed some decisions. 
    The EPA did not estimate the increased processing time. The
agency said it expedites reviews of lower-risk products.  
        Farm chemical companies spent 6.2% of sales revenue on
development of new active ingredients in 2020, down from 8.9% in
2000, AgbioInvestor said. Its data showed the introduction of
new active ingredients fell by more than half in 2022 from 2000.
    Instead, companies have expanded uses of existing products
like dicamba, glufosinate and 2,4-D.  
    FMC plans the 2026 launch of an herbicide to kill grassy
weeds in rice crops based on the industry's first new mode of
action, a term for the way a chemical kills a weed, in three
    The herbicide was in development for 11 years. FMC hopes it
will generate $400 million in sales within a decade, a fraction
of the roughly $8 billion global glyphosate market.
    "If we don't keep developing the new products, we are going
to run into a wall where growers don't have the tools to combat
the pests," CEO Mark Douglas said. "And then ultimately you face
food security issues."
    The world's biggest agriculture chemical and seed company,
Germany's Bayer, hopes to produce its first new mode of action
herbicide in over 30 years by 2028.
        "We're really desperate for (new modes of action) if
we're going to sustain uses for farmers," said Bob Reiter, head
of research and development for Bayer's crop science division.
    Two decades ago, companies commercialized a product for
every 50,000 candidates, but it now takes 100,000 to 150,000
attempts, Reiter said. 
    U.S.-based Corteva said it has incorporated sustainability
criteria, such as reduced groundwater risk, in its research and
development, aiming to clear the path with regulators.
        It hopes that approach will shorten the regulatory
process when it introduces a fungicide with a new mode of action
against Asian soybean rust disease in Brazil around 2027, said
Ramnath Subramanian, vice-president of crop protection research
and development. He did not say how much shorter the process may
    Bill Freese, scientific director of the Center for Food
Safety in Washington, said farmers should shift away from crops
genetically engineered to tolerate herbicides, which lead to
plants becoming resistant to multiple chemicals through repeated
    "It's like this toxic spiral," Freese said. "There's no end
in sight." 

 (Reporting by Rod Nickel in Winnipeg, Manitoba and Tom Polansek
in Chicago; Editing by Caroline Stauffer and Suzanne Goldenberg)
 ((rod.nickel@tr.com; Twitter: @RodNickel_Rtrs;))


The views and opinions expressed herein are the views and opinions of the author and do not necessarily reflect those of Nasdaq, Inc.

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