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Washington Tuesday, November 10, 2026

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Corn & Soy

APHIS takes comments to Jan. 8 on Pioneer's COR121 corn, a lepidopteran trait built on a fern protein instead of Bt

USDA's draft risk assessment finds the corn unlikely to pose more plant pest risk than conventional corn. Its IPD083Cb protein binds different gut sites than Bt proteins, which matters where corn earworm and fall armyworm have outlasted Bt traits.

By Commodity Hill Staff6 min read

“COR121 maize is unlikely to pose an increased plant pest risk compared to the unmodified corn.” That is the conclusion of the draft risk assessment the Animal and Plant Health Inspection Service (APHIS) released November 9 with Pioneer Hi-Bred International’s petition to deregulate COR-ØØ121-4 corn[1]. The corn carries an insecticidal protein from a fern rather than from Bt bacteria, aimed at caterpillar pests of corn. APHIS is taking comments through January 8, 2027[1].

What APHIS published

The notice, in Docket APHIS-2026-1288, covers APHIS Petition Number 26-084-01p[1]. Pioneer asks for a determination of nonregulated status under 7 CFR part 340, the rules APHIS uses under the Plant Protection Act to oversee genetically engineered organisms that may be plant pests[1]. COR121 was engineered to express two proteins[1]:

  • IPD083Cb, for protection against certain susceptible lepidopteran pests
  • Phosphomannose isomerase (PMI), a selectable marker used in the lab to identify transformed plants

APHIS’s draft plant pest risk assessment compared COR121 with the unmodified corn it was derived from[1]. The agency asks commenters for biological and ecological information in particular, and encourages them to submit data and studies[1]. After the comment period, APHIS will approve or deny the petition, post its determination on its website and publish a notice in the Federal Register[1].

The review runs on narrower ground than it did a few years ago. Since July 9, 2025, APHIS has not prepared a National Environmental Policy Act analysis alongside these petitions. It first asks whether the organism is a plant pest, and if the answer is no, it ends the review because it lacks jurisdiction[7]. That policy change, and how it played out for the Darling 54 chestnut, was covered in earlier coverage.

Why a fern protein matters for Bt-resistant earworms

IPD083Cb comes from the giant maidenhair fern, Adiantum trapeziforme var. braziliense[11]. Food Standards Australia New Zealand (FSANZ) describes it as an 853-amino-acid protein that damages the gut lining of susceptible caterpillars much as Bt Cry proteins do, but binds different receptor sites in the midgut than Cry2A.127, Vip3Aa or a Cry1Ab variant[11]. FSANZ concluded from that difference that IPD083Cb “is unlikely to share cross-resistance” with insects resistant to Cry proteins[11].

EPA reached a similar picture from the structure side. In its May 2026 tolerance rule, the agency said fern-derived IPD proteins “share no significant sequence homology to Cry proteins” but closely resemble domains I and II of three-domain Cry proteins in structure and function, with activity specific to lepidopteran pests[9].

The field evidence so far is the developer’s. Corteva Agriscience scientists, writing in Toxins in 2019, reported that corn expressing IPD083Cb reduced ear damage from natural corn earworm infestations at three U.S. field sites[13]. In laboratory work, Cry1Fa-resistant fall armyworm ate leaf disks producing the Bt protein Cry1Fa, while disks producing IPD083Cb were almost fully protected against both resistant and susceptible insects[13]. Because the fern proteins recognize different midgut target sites, the authors judged cross-resistance with commercial Bt proteins unlikely[13].

In the field

For corn growers, the trait’s value depends on how it reaches the seed bag. EPA proposed changes to its resistance-management requirements for lepidopteran plant-incorporated protectants in 2020, under Docket EPA-HQ-OPP-2019-0682, after Bt resistance had turned up in corn and cotton in some locations, according to a Wiley Rein summary[15]. The law firm noted that some of the proposed changes could weigh heavily on companies selling Bt traits and on growers using them[15].

The Center for Science in the Public Interest (CSPI) went further in its comments on that docket. It cited EPA’s Scientific Advisory Panel finding that it is “highly likely that H. zea will further evolve resistance to Bt crops on a broad scale in the continental U.S.” without more action, and urged EPA to end sales of single-trait lepidopteran corn within two years[14]. CSPI defined a single-trait product as one with a single toxin that kills the target pest, and argued that such products speed resistance because no second toxin is there to kill survivors[14].

COR121, as petitioned, carries one insecticidal protein[1]. That cuts both ways for a grower. A protein that binds new gut sites could kill earworms and armyworms that survive today’s Bt proteins[11, 13]. Planted alone, though, it would fit CSPI’s definition of the single-trait product it wanted off the market[14]. The record this piece draws on does not show how Pioneer plans to package the event.

Other details from the safety files bear on how the corn would move through grain channels:

  • FSANZ found a single copy of the inserted genes at one site in the genome, stably inherited, with no antibiotic resistance marker genes[11].
  • Grain from COR121 showed no statistically significant difference from its control in 57 compositional analytes, from field trials at 8 sites in the United States and Canada in 2024[11].
  • FSANZ concluded that food from COR121 is as safe as food from conventional corn[11]. The application there was filed by Corteva Agriscience Australia on Pioneer’s behalf[12].
  • EPA has already exempted IPD083Cb residues from tolerance requirements on all food and feed commodities when used as a plant-incorporated protectant[9].

Export clearance in other buyer countries is not covered in the record this piece draws on.

Soybeans and cotton are in the same queue

COR121 is the second Pioneer petition this year built on IPD083Cb. In August, APHIS opened comments on COR-23134-4 soybean, which pairs IPD083Cb with two Bt proteins, Cry1B.34.1 and Cry1B.61.1; that comment period closed October 19[5]. EPA’s May tolerance exemption was written for that soybean, and it covers IPD083Cb in all food and feed commodities[9]. EPA said the protein showed no toxicity to mice at oral doses totaling 5,000 mg/kg body weight and had no meaningful similarity to known allergens[9].

The corn petition joins a run of lepidopteran traits before APHIS. In February the agency opened comments on Pioneer’s DP-910521-2 corn, with a Cry1B.34 protein and glufosinate tolerance, Pioneer’s DAS-01131-3 corn and Syngenta’s MZIR260 corn, which targets fall armyworm[2, 3, 4]. Those comment periods closed April 20, 2026[2]. Bayer’s MON 89151 cotton, with three insecticidal proteins, is open for comment through November 20, 2026, under Docket APHIS-2026-0859[8].

On the Hill and at EPA

No congressional action is tied to this petition. The decision path runs through two agencies under separate laws.

APHIS rules on plant pest status under the Plant Protection Act[1]. EPA registers the insecticidal protein itself under the Federal Insecticide, Fungicide, and Rodenticide Act. EPA logged Pioneer’s application for “COR121 Maize,” EPA File Symbol 29964-GI, on December 22, 2025, under Docket EPA-HQ-OPP-2026-1255, listing IPD083Cb as an active ingredient not found in any currently registered product[10]. EPA stated that the notice “does not imply a decision” on the application and that some registration actions get a further comment round on the proposed decision[10].

Opposition in the record so far is thin. The single comment on EPA’s tolerance petition urged a ban on plant-incorporated protectants, citing gene flow; EPA answered that its assessments found no evidence PIP genes or toxins transfer to microorganisms or other fauna[9]. APHIS’s last insect-trait corn decision drew 11 comments, five of them general opposition to genetic engineering and four from organizations supporting deregulation[6].

When will APHIS decide on COR121 corn?

APHIS gives no target date[1]. The closest guide is Bayer’s MON 95275 rootworm corn: comments ran July 8 to September 8, 2025, and APHIS recognized its nonregulated status as of March 19, 2026, a little over six months later by this report’s count[6].

  • January 8, 2027: Comments close on Docket APHIS-2026-1288[1].
  • After that: APHIS determination notice in the Federal Register; no date set[1].
  • EPA: Registration decision on File Symbol 29964-GI, with a possible comment round on a proposed decision[10].

The three corn petitions APHIS put out for comment in February, whose comment periods closed April 20, had no published determination as of November 9[2].