Independent trials for the recently authorised cereal fungicide Plaxium reveal that the three-way mix gave strong broad-spectrum disease control across winter wheat and winter barley.

In autumn 2023, Bayer launched the SDHI active isoflucypram, which is marketed in Britain as Vimoy, and sold in a co-pack with the widely used azole prothioconazole.

This new three-way formulation, called Plaxium, sees the SDHI in a mixture with fluopyram and prothioconazole. Bayer says it offers robust activity in the convenience of a co-formulation.

As part of its ongoing fungicide trials, the AHDB tested the product under code in crops of winter wheat and winter barley for a range of diseases during 2019, 2020 and 2021 harvest trial work.

See also: New cereal fungicide mix available for spring 2025

Performance in wheat

In wheat, Plaxium was evaluated for its efficacy against Septoria tritici, brown rust and yellow rust.

This was compared to existing fungicide standards, with data averaged over the three-years.

The fungicide was highly effective against septoria, in both protectant and eradicant situations, performing comparably to existing standards.

In terms of yield, Plaxium gave a comparable yield response to both Univoq and Revystar XE and a 0.3t/ha increase compared with Ascra Xpro at the full label rate.

On yellow rust, Plaxium’s activity was above Ascra Xpro and Revystar, comparable to Univoq and close to Elatus Era.

These differences carried through to harvest, with Plaxium-treated plots yielding comparably to Univoq.

Trials revealed superior brown rust control, compared with the other mixture products tested and was comparable in efficacy to Imtrex and Elatus Plus.

Plaxium achieved a yield response comparable to Revystar and higher than the other products tested.

Since 2021, changes in the brown rust population appear to have reduced the field activity of at least one SDHI, namely benzovindiflupyr (Elatus Plus).

It is currently unclear if other SDHIs have been affected.

Niab’s Stuart Knight, who works on the trials, said: “The wheat trials indicate a clear efficacy and yield-response advantage for Plaxium compared to Ascra Xpro.

“This reflects the boost to foliar disease activity provided by isoflucypram, in place of bixafen, in this three-way mixture.”

Performance in barley 

In the winter barley trials, Plaxium was evaluated for its efficacy against rhynchosporium, net blotch, ramularia and powdery mildew. It showed good efficacy against all four diseases.

SRUC’s Fiona Burnett, trial partner and chairwoman of the UK Fungicide Resistance Action Group (Frag), said: “Plaxium adds another robust mixture option for the control of barley diseases and is carefully stewarded to manage resistance risk.”

Against rhynchosporium, in both protectant and eradicant situations, Plaxium gave excellent disease control, comparable to or better than Siltra Xpro and Ascra Xpro, and similar to the control provided by the solo active product Miravis Plus.

Similarly, against net blotch, Plaxium showed a very high level of efficacy, even at 50% of the label rate, performing comparably to Miravis Plus and Ascra Xpro.

Control of ramularia with Plaxium matched that obtained with Revystar XE and was slightly better than Ascra Xpro.

Plaxium gave the highest level of protectant activity against powdery mildew of the broad-spectrum products tested, although disease pressure was relatively low in these trials.