Update — September 2026: This article has been corrected to accurately describe icafolin-methyl’s mode of action as inhibition of plant tubulin polymerisation. An earlier version incorrectly described it as an ACCase inhibitor. We have also updated the article to reflect Bayer’s subsequent application for regulatory approval of icafolin-methyl in Australia.
Not All Herbicides Are Created Equal
Herbicides don’t all work the same way. Glyphosate interferes with one part of plant biology; Icafolin targets something else entirely.
And if you’ve been hearing Icafolin described as the “new alternative,” it’s natural to wonder what actually separates the two — beyond the marketing.
And understanding how Icafolin herbicide works — especially compared with glyphosate — matters, because these differences will shape how it’s used in New Zealand.
The truth is, their differences run deeper than chemical families or molecular targets. They reflect two very different approaches to weed control, each with its own risks, limitations, and consequences.
So let’s take a closer look.
Not just at how these herbicides work, but at what those differences really mean for soil health, resistance, and the future of weed control here in New Zealand.
Because “new” doesn’t automatically mean better.
Sometimes it just means… new.
How Glyphosate Works — and Why It’s Being Replaced
Most people know glyphosate as the active ingredient in Roundup®. It works by blocking the EPSPS enzyme in the shikimate pathway — a process plants rely on to make essential amino acids. When that pathway is disrupted, the plant can’t function or grow. It slowly shuts down.
One of the reasons glyphosate became so dominant is its broad-spectrum nature. It isn’t fussy about what it kills. Grass, broadleaf weeds, emerging seedlings — it takes out almost anything green. For large-scale agriculture, that simplicity was a game changer. One product. Predictable outcomes. Fewer passes across a paddock.
But the more a single chemical is used, the faster nature adapts. After decades of heavy reliance, more than 50 weed species worldwide are now resistant to glyphosate. Some regions are already battling “superweeds” that shrug off doses multiple times higher than the label ever intended.
And once resistance spreads, everything built around glyphosate starts to wobble — cropping systems, spray schedules, and the economics of weed control. That’s why the industry is scrambling for new “modes of action.” Icafolin is Bayer’s attempt to fill that widening gap, not because it solves glyphosate’s flaws, but because the system needs another chemical to keep running.
Replacing one mechanism with another doesn’t fix the underlying problem.
It just buys time — until resistance catches up again.
How Icafolin Works — and What Makes This New Herbicide Different
Icafolin-methyl belongs to a new chemical class known as isoxazolin carboxamides and works very differently from glyphosate.
After entering the plant, icafolin-methyl is converted to icafolin. Research published in Pest Management Science found that both compounds inhibit plant tubulin polymerisation, probably by binding to β-tubulins.
Tubulin is a protein used to build microtubules — structures that are essential for processes including cell division. Disrupting the formation of those microtubules interferes with normal plant growth and ultimately kills the weed.
That makes the terminology around Icafolin slightly more complicated than Bayer’s description of a “new mode of action” might suggest. Tubulin polymerisation inhibition itself is not new; other herbicides already act through this mechanism. The researchers who characterised Icafolin describe it as having an established mode of action, but say its chemistry, potency, weed spectrum and effectiveness after foliar application distinguish it from existing tubulin-inhibiting herbicides.
That distinction matters. A new chemical with unusual properties is not necessarily the same thing as discovering an entirely new biological target.
And, as always, a different mechanism does not by itself tell us whether a herbicide is safe. That requires toxicological, environmental and exposure data of its own.
What Icafolin Doesn’t Replace: Glyphosate’s Pre-Harvest Spraying Role
This is the part of the conversation that often gets left out. Icafolin is being introduced as a replacement for glyphosate in weed control, but it can’t replace one of glyphosate’s most controversial roles: ending a crop’s life just before harvest.
For decades, glyphosate has been used to dry down food crops on purpose. Wheat, oats, barley, peas, canola — all can be sprayed a few days before harvest to force uniform ripening and speed up drying. It’s a management shortcut that fits neatly into tight processing schedules and modern supply chains.
And it’s also one of the most direct ways glyphosate ends up in food.
But as of 30 October 2025, New Zealand’s Ministry for Primary Industries (MPI) introduced new rules banning pre-harvest glyphosate use on cereals grown for human consumption. Wheat, barley, and oats can now only be sprayed before the crop emerges from the soil.
It’s a significant shift — and one the public has been calling for — but it doesn’t solve everything. Other crops, like canola and many legumes, are still allowed to be desiccated with glyphosate. And no other chemical, including Icafolin, performs the same job at harvest. Icafolin doesn’t dry crops or move through plant tissues the way glyphosate does. In fact, one of its selling points is that dead weeds stay upright, creating a kind of mulch effect… the opposite of what’s needed for rapid harvest.
So while headlines focus on Icafolin’s “new mode of action,” the food-residue side of glyphosate use remains unresolved — especially for crops not covered by MPI’s decision.
We dive deeper into that issue in our related article:
The Desiccation Dilemma: Why Glyphosate’s Real Role Is Hard to Replace
A New Herbicide, Same Industrial Farming Model
Icafolin isn’t being introduced to support organic growers, home gardeners, or regenerative systems. It’s being introduced to keep yields up in a farming model that’s already heavily dependent on chemical inputs. In that context, a new herbicide isn’t a shift in philosophy — it’s a continuation of the same logic that has shaped industrial agriculture for decades.
This is why “innovation” in herbicides so often looks like reinforcement rather than change. The goal is to maintain productivity within an existing framework: large-scale monocultures, tight harvest windows, uniform crops, and heavy reliance on chemical control. The operating assumption is that weeds must be eliminated quickly, efficiently, and across vast areas — and that chemicals are the fastest way to do it.
A different herbicide chemistry and mode of action from glyphosate doesn’t challenge that; it simply sustains it. Glyphosate was once marketed as a breakthrough. Icafolin will be positioned the same way. But both exist to keep the same machine running, even as resistance, soil decline, and public concern continue to grow.
And that’s what makes this moment so important. When resistance pushes the industry toward new actives, we have an opportunity to step back and ask larger questions. Not just, “What else can we spray?”
But “What else is possible?”
Australia Moves Toward Icafolin Herbicide Approval — What Does That Mean for New Zealand?
Bayer has now applied for regulatory approval of Icafolin-methyl in Australia, with a commercial launch targeted from 2028, subject to APVMA approval. Australia has been designated a “Priority One” market, partly as a result of Bayer’s partnership with the Grains Research and Development Corporation (GRDC).
This tells us something important. It’s not just a technical timeline. It’s a strategic one. Bayer is moving quickly to secure footholds in large agricultural economies before glyphosate resistance becomes unmanageable. Icafolin isn’t being developed as a niche product — it’s being positioned as an important new tool for weed control as resistance to existing herbicides grows.
So what does that mean for New Zealand?
In theory, nothing immediate. Icafolin isn’t yet under EPA review here, and New Zealand often takes longer to approve new agrichemicals. But Australia’s early uptake will create pressure. Once growers there begin adopting Icafolin, the message will quickly shift: “If Australia is using it, why aren’t we?”
And that’s the concern.
Because the narrative won’t be about alternatives to chemicals or transitions to better systems. It will be about keeping pace — keeping yields high, keeping weeds manageable, and keeping the chemical status quo alive for another cycle.
Meanwhile, Back in New Zealand…
Here in New Zealand, we’re not locked into the same trajectory Australia is on. We actually have room to pause and ask a different kind of question — not which chemical comes next, but whether the model itself needs to keep leaning on chemicals at all.
There are already growers here proving that a different path is possible. Some are using biological inputs, mechanical tools, crop rotation, diverse planting systems, and careful timing to manage weeds without relying on the next label or formulation. They’re building resilience into their soil instead of fighting weeds with ever-stronger chemistry. And importantly, they’re doing it without waiting for industry to hand them a new product.
The question is: why are they still the minority?
What would it look like if these growers weren’t treated as outliers, but as early adopters of a more resilient approach? What if public funding — the same kind that has historically supported chemical-based systems — backed the transition toward lower-input, soil-building, truly regenerative methods?
Because we’ve heard the promises before.
Glyphosate was once framed as a breakthrough. So were organophosphates. And now Icafolin will be marketed with its own reassuring language: new mode of action, plant-specific, reduced risk. Each wave arrives with the same story. And each time, we learn the full picture only after the chemicals have already shaped our landscapes, our soils, and sometimes our health.
New Zealand doesn’t have to keep repeating that cycle.
We don’t have to wait for residues to rise, or for resistance to spread, or for the next chemical to come knocking before we ask better questions.
We can choose a different direction now — if we want to.
This article is part of a mini-series exploring what’s replacing glyphosate—and why it might not be the revolution we’re being sold.
- Part 1: Icafolin — Bayer’s New Herbicide & the Next Glyphosate Alternative?
- Part 2: The Desiccation Dilemma: Why Glyphosate’s Real Role Is Hard to Replace
- Part 3: You are here — How Icafolin Herbicide Works—And Why It’s Not Just Another Glyphosate
- Part 4: Beyond the Withdrawal: What Comes (and What Doesn’t) After Glyphosate
Related Series
This article is part of a broader exploration of how chemical regulation works in New Zealand — and how often it doesn’t.
If you’re wondering why glyphosate got so entrenched in the first place — and how alternatives like Icafolin are slipping in with little public scrutiny — you might want to start here:
Ignored PCE Warning: NZ Chemical Monitoring
A 3-part mini-series examining how the system failed to act on the Parliamentary Commissioner for the Environment’s warnings about toxic chemical oversight.
Resources & References
Before You Go Down the Rabbit Hole…
It’s easy to get swept up in the hype of a “new mode of action.” But as the references below reveal, Icafolin is more than a chemical — it’s a strategic response to a failing system. These sources don’t just explain how Icafolin works; they help us understand why it’s being fast-tracked, who stands to benefit, and what narratives are being used to sell it.
Because the real story isn’t just about science. It’s about systems, assumptions, and the kind of future we’re being nudged toward — one label at a time.
Bayer targeting 2028 for Australian launch of Icafolin, a groundbreaking new herbicide from a new chemical class
(Bayer Australia, 30 September 2025)
This press release outlines Bayer’s plan to submit its novel herbicide, icafolin‑methyl, for regulatory approval in Australia in 2026, with a commercial target date of 2028. Australia is designated a “Priority One” market in Bayer’s global roll‑out strategy, reflecting the weed‑resistance pressures in its grain sector.
Bayer submits registration applications for novel herbicide in four major markets
(Bayer, 30 July 2025)
This company press release outlines how Icafolin‑methyl has been filed for regulatory approval in the EU, U.S., Canada and Brazil, representing what Bayer claims is agriculture’s first new herbicide mode of action in over 30 years. The filing signals the global scale of the push to replace—or at least supplement—Glyphosate.
Herbicide Resistance – Overview
(Herbicide Resistance Action Committee)
This resource explains how weed populations evolve to survive herbicide treatments, how repeated use of the same mode of action drives resistance, and why new chemistries like Icafolin don’t automatically secure long‑term protection.
Hazardous Substance Classification System
New Zealand EPA
An overview of how the EPA classifies and approves agrichemicals like glyphosate or Icafolin in New Zealand under the HSNO Act.
The Desiccation Dilemma: Why Glyphosate’s Real Role Is Hard to Replace
No More Glyphosate NZ
A companion article exploring why Icafolin doesn’t replace glyphosate in pre-harvest crop drying—and what that means for food safety and future regulation.
Icafolin and Glyphosate—Two Chemicals, One Broken Model
No More Glyphosate NZ
Introduces the Icafolin mini-series and unpacks why replacing glyphosate with new chemical solutions may not solve the deeper issues in industrial agriculture.
Still Have Questions? Good.
The resources above aren’t here to give you the final word — they’re an invitation to think more critically. To read between the lines of regulatory announcements. To compare what’s said in press releases with what’s missing in safety studies. To look beyond chemical swaps and ask: What kind of agriculture are we protecting?
That’s where real change begins. Not with the next product. But with the next question.
Image Source & Attribution
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