Bayer Engineered a New Corn Seed That’s Resistant to Five Herbicides. But How Long Will It Work?

Johnathan Hettinger July 18, 2020

A farmer sprays the herbicide glyphosate on a corn field.

Edi­tor’s Note: This sto­ry was orig­i­nal­ly pub­lished by the Mid­west Cen­ter for Inves­tiga­tive Report­ing.

A new genet­i­cal­ly engi­neered corn seed designed by Bay­er to be sprayed by up to five her­bi­cides could rep­re­sent the future of farm­ing, pro­vid­ing grow­ers with more pes­ti­cides to com­bat the prob­lem of weed resistance.

But for how long? That’s the ques­tion raised by weed sci­en­tists, who say farm­ers need to start switch­ing to non-chem­i­cal options to keep weeds under control.

Over the past 50 years, weed resis­tance has become a sig­nif­i­cant prob­lem for agri­cul­ture in the U.S., with more than 165 unique species of weeds becom­ing resis­tant to chem­i­cals. The prob­lem has increased sig­nif­i­cant­ly since the intro­duc­tion of genet­i­cal­ly mod­i­fied crops and use of accom­pa­ny­ing her­bi­cides in the 1990s. 

The new seed, which Bay­er has peti­tioned the U.S. Depart­ment of Agri­cul­ture for approval, could be sprayed by glyphosate, glu­fos­i­nate, dicam­ba, 2,4‑D and quizalo­fop, giv­ing farm­ers mul­ti­ple options for weed control.

Bay­er spokes­woman Susan Luke said in an email that, pend­ing reg­u­la­to­ry approvals, the com­pa­ny plans a full com­mer­cial launch of the seed lat­er this decade.

We expect HT4 to be wide­ly used – and grow­ers con­tin­ue to ask for addi­tion­al crop pro­tec­tion tools to help man­age tough-to-con­trol weeds. This prod­uct will offer grow­ers more options to man­age broadleaf weeds in corn and will pro­vide grow­ers increased flex­i­bil­i­ty and anoth­er tool in the crop pro­tec­tion tool­box,” Luke said.

Corn is the most boun­ti­ful crop grown in the Unit­ed States, mak­ing up about 92 mil­lion acres of farm­land, an area about the size of Min­neso­ta or Michi­gan; about a third of the crop is used for ani­mal feed, about a third is used for ethanol and the rest is split between human food, bev­er­ages, indus­tri­al uses and exports. About 90 per­cent of corn grown in the U.S. is genet­i­cal­ly mod­i­fied, accord­ing to the USDA.

The prod­uct comes at a time when Bay­er, which acquired agribusi­ness giant Mon­san­to in 2018, and its pes­ti­cides are under scrutiny.

In June, Bay­er announced a $10 bil­lion set­tle­ment of claims that glyphosate, the active ingre­di­ent in Roundup, caus­es can­cer. The com­pa­ny also announced a $400 mil­lion set­tle­ment of claims that dicam­ba, a her­bi­cide sold by Bay­er and Ger­man agribusi­ness com­pa­ny BASF, has drift­ed and harmed thou­sands of oth­er farmers.

By pur­chas­ing Mon­san­to, Bay­er acquired some of the most pop­u­lar crop­ping sys­tems in the U.S.

Monsanto’s Roundup Ready crops, engi­neered to be resis­tant to the her­bi­cide Roundup, quick­ly became ubiq­ui­tous after being intro­duced in the 1990s. Glyphosate, the active ingre­di­ent, is the most com­mon­ly used her­bi­cide in the U.S., but as the amount sprayed in crops increased 40-fold between 1992 and 2016, the num­ber of weeds resis­tant to glyphosate grew. Over the past 25 years, the num­ber of weeds resis­tant to glyphosate has increased from zero to more than 45, accord­ing to the Inter­na­tion­al Sur­vey of Her­bi­cide Resis­tant Weeds.

In response, agribusi­ness com­pa­nies have released crops engi­neered to be resis­tant to oth­er her­bi­cides: Mon­san­to launched its Roundup Ready II crops, engi­neered to be resis­tant to glyphosate and dicam­ba; BASF launched its Lib­er­ty crops, designed to be resis­tant to glyphosate and glu­fos­i­nate; Corte­va Agri­science, for­mer­ly DowDupont, released Enlist crops, designed to be resis­tant to glyphosate, 2,4‑D and quizalofop.

The new Bay­er tech­nol­o­gy com­bines all of these tech­nolo­gies into one. The new prod­uct is not designed to be sprayed by all five weed killers at once, but instead to help stream­line the cur­rent agri­cul­tur­al sys­tem, allow­ing seed deal­ers to car­ry one seed that gives farm­ers a choice on which com­bi­na­tion of weed killers they want to spray.

It’s not a big rev­o­lu­tion. It’s the way things are mov­ing,” said Robert Hartlz­er, a weed sci­ence pro­fes­sor at Iowa State University.

This phe­nom­e­non is often called the pes­ti­cide tread­mill” — as more weeds devel­op resis­tance to more her­bi­cides, new and bet­ter her­bi­cides are needed. 

The accel­er­a­tion seems to be get­ting faster and faster, said Kristin Schafer, exec­u­tive direc­tor of the Pes­ti­cide Action Net­work. PAN is orga­niz­ing cit­i­zens to sub­mit com­ments against the new Bay­er tech­nol­o­gy, say­ing the crop­ping sys­tem would be more ben­e­fit­ed by switch­ing to crop rota­tions, more bio­di­ver­si­ty on the farm and increased soil health.

This five-trait corn is absolute­ly the oppo­site direc­tion of the way we need to be going,” Schafer said.

Some weeds are already start­ing to show signs of resis­tance to dicam­ba, which has increased sig­nif­i­cant­ly in use since Mon­san­to intro­duced new cot­ton and soy­bean seeds resis­tant to the her­bi­cide begin­ning in 2015. Dicam­ba has also caused wide­spread dam­age to the envi­ron­ment because it is hard­er to control.

Hart­zler warned that weeds are quick­ly out­pac­ing tech­no­log­i­cal devel­op­ments. Weeds have already devel­oped resis­tance to each of the her­bi­cides includ­ed in the tech­nol­o­gy, though they are still very effec­tive across the Unit­ed States.

It’s real­ly going to be a short-term fix, but at this point in time, it’s what fits the cur­rent pro­duc­tion sys­tem best,” Hartlz­er said.

Aaron Hager, a weed sci­ence pro­fes­sor at the Uni­ver­si­ty of Illi­nois, found in a 2015 study that using mul­ti­ple her­bi­cides to kill weeds is bet­ter at delay­ing resis­tance than switch­ing from one her­bi­cide one year to a dif­fer­ent the next. Bay­er point­ed the Mid­west Cen­ter to that study and said the new seed will help delay resistance.

But Hager said the way that weeds are resis­tant to her­bi­cides is changing. 

Her­bi­cides work by tar­get­ing a spe­cif­ic mech­a­nism in a plant and dis­rupt­ing that mech­a­nism. For the past 30 years, weeds have large­ly start­ed to devel­op resis­tance at the tar­get site, shift­ing the way they grow and no longer allow­ing her­bi­cides to bind to the plant. 

But increas­ing­ly, plants have start­ed to devel­op meta­bol­ic resis­tance, which is when the plant’s inter­nal mech­a­nisms are able to metab­o­lize her­bi­cides into non-tox­ic prod­ucts, mak­ing them inef­fec­tive. The mech­a­nism is sim­i­lar to crops that are able to sus­tain being sprayed by herbicides.

We’re in anoth­er era now,” Hager said. We’re try­ing to under­stand what has changed and allows them to func­tion more like the crop.”

With meta­bol­ic resis­tance, weeds can devel­op resis­tance to her­bi­cides that they haven’t been exposed to before, Hart­zler said. 

Bay­er said that these chem­i­cals are need­ed. Even with best prac­tices, corn can see a 52 per­cent yield loss with­out a her­bi­cide being sprayed, accord­ing to a study by the Weed Sci­ence Soci­ety of Amer­i­ca. Hager said that farm­ers won’t stop using chem­i­cals, but they can use them along with oth­er options.

Both Hager and Hart­zler said they are rec­om­mend­ing farm­ers increas­ing­ly use non-chem­i­cal options. Hart­zler said places like Aus­tralia are start­ing to use com­bines that can help destroy weed seeds, so they don’t con­tin­ue to grow.

I know that it’s going to change in the rel­a­tive­ly near future sim­ply because even the addi­tion of these new her­bi­cide traits is not going to solve the resis­tance prob­lem,” Hart­zler said.

The Mid­west Cen­ter for Inves­tiga­tive Report­ing is a non­prof­it, online news­room offer­ing inves­tiga­tive and enter­prise cov­er­age of agribusi­ness, Big Ag and relat­ed issues through data analy­sis, visu­al­iza­tions, in-depth reports and inter­ac­tive web tools. Vis­it us online at www​.inves​ti​gatemid​west​.org

Johnathan Het­tinger is a jour­nal­ist based in Liv­ingston, Mon­tana. Orig­i­nal­ly from Cen­tral Illi­nois and a grad­u­ate of the Uni­ver­si­ty of Illi­nois, he has worked at the Mid­west Cen­ter for Inves­tiga­tive Report­ing, the Liv­ingston Enter­prise and the (Cham­paign-Urbana) News-Gazette. Con­tact Johnathan at jhett93@​gmail.​com and fol­low him on Twit­ter @jhett93.
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