While discovering new active ingredients still requires extensive screening, digital tools are set to speed up the process, removing the element of luck. The launch of Bayer’s new fungicide, Iblon, in London marked the first of these intelligently designed molecules.

“Stewardship is an individual responsibility for the collective good.”

By Lucy de la Pasture

Just like London buses, registrations of new fungicide molecules have been coming one behind the other over the past couple of years, after what has been a fairly long hiatus. So it was fitting that the UK’s capital hosted the recent launch of isoflucypram, branded as Iblon, which also marked the first European regulatory approval.

Ironically, farmers in the European Union will have to wait at least another three years before they have access to the new wheat fungicide. The UK’s Chemicals Regulation Division (CRD) acted as the Rapporteur Member State responsible for evaluating the active substance and producing a draft assessment report for its fellow member states, at that time, to consider. After Brexit, France took over that function and the decision was made to ignore the work done by CRD and start the evaluation process again, which is why they are so far behind the UK which accepted its own report.

The active substance belongs to the succinate dehydrogenase inhibitor (SDHI) group of chemistry and offers a step-change from Bayer’s pioneering cereal SDHI, Aviator Xpro (bixafen+ prothioconazole) – first launched in the UK 2011 and subsequently combined with SDHI active, fluopyram, as Ascra Xpro in 2016.

According to Michael Maue, Bayer’s global project lead, the “unrivalled biological efficacy” of Iblon is due to its unique molecular structure. It has an N-cyclopropyl ring at its centre, and it’s this that makes a difference at its target binding site in the pathogen. In the field this translates to efficacy on a range of diseases, notably septoria and rusts, and distinguishes the active as a new subclass of SDHI chemistry.

The structure of the isoflucypram molecule was a deliberate design process and the addition of the N-cyclopropyl ring transformed its efficacy, he added.

As well as Iblon’s intrinsic activity, Michael highlighted the new fungicide’s formulation as the second factor giving it good field performance. “A fungicide formulation needs to give the active ingredient the ability to penetrate the waxy leaf layer into the upper epidermis, so it’s protected against environmental stresses – such as rain – and it’s available for systemic transport in the leaf to better protect the plant. It should also have good spreadability on the leaf surface. These are both optimised in Iblon’s formulation.”

The regulatory requirements in the European Union – mirrored in the UK’s own regulations since Brexit – have tightened under its hazard-based criteria, adopted in 2009. Active ingredients have been lost as their registrations come up for review and the flow of new molecules through the pipeline has slowed. Iblon’s own journey began 15 years ago, and Michael described its development path as “complicated, with a few potential show-stoppers” which the Bayer team navigated by finding scientific answers to the regulatory questions posed.

In addition to Iblon’s performance on many of the diseases that trouble wheat crops in the UK, the emphasis at the launch was as much about resistance management to preserve its efficacy for years to come.

SRUC’s Professor Fiona Burnett welcomed the new chemistry and rated its performance as very similar to the other new fungicide actives on septoria. “The UK is very reliant on multiple applications of a limited palette of chemistry. Iblon is an exciting new tool, but let’s think about how we steward it going forward,” she said.

“Since the strobilurins [which totally succumbed to resistance in the 2003 season], we’ve developed much better ways of managing chemistry from a resistance perspective. Trials show that what is done on an individual farm really matters when it comes to pathogen shifts in sensitivity,” she said.

“Dose is the ultimate choice to be made in the field – using appropriate balanced mixtures, alternating and mixing fungicide modes of action, and reducing but not splitting fungicide doses. Diversifying, with a new SDHI to add to programmes, brings benefits,” she said.

Fiona warned that its time for individuals to take responsibility as its their actions that will ultimately decide the longevity of the products available to them. “Stewardship is an individual responsibility for the collective good,” she emphasised.

New Zealand farmers were the first to benefit from Bayer’s new fungicide chemistry, with its regulatory authorities granting approval for use in the 2019-2020 season.

Bringing his experience of Iblon to the launch, NZ farmer Eric Watson outlined his farming system on the Canterbury Plains and amazing video footage brought this to life with the Southern Alps forming a stunning backdrop.

Eric’s appetite to regain his Guiness World Record for wheat yield, snatched from him last year by UK grower Tim Lamyman, was evident. With two world records already under his belt – recording 17.398 t/ha in 2020, beating his previous record of 16.791 t/ha in 2017 – Eric believes Iblon will be instrumental in his next attempt to regain the record he covets. To beat his UK rival, he said, it just needs the right amount of sun, at the right time…

This article was taken from the latest issue of CPM. Read the article in full here.

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