New Syngenta wheat fungicide formulated with epoxiconazole

Syngenta’s SDHI fungicide for wheat, like Aviator Xpro, will be targeted at the T2 flag leaf timing, if approved for the 2011 season.

Its long-lasting activity against key wheat diseases combined with a lack of systemic movement to new leaf growth made it fit best at that timing, David Ranner, the firm’s cereals fungicide technical manager, said at one of over 20 events introducing the product directly to growers and advisers.

Isopyrazam, the SDHI fungicide active already available in the barley product Bontima, also provided some curative activity against septoria, he said.

It wasn’t enough to replace triazole fungicides, which should always form the backbone of programmes, but the combination would give as good a curative activity as was possible, he said.

For that reason, Syngenta had decided to formulate isopyrazam with epoxiconazole for wheat rather than releasing it as straight isopyrazam, he said.

The two were closely matched in their activity on the disease spectrum, which helped protect against resistance development. “To have protection you want both actives to work on the same diseases, otherwise you expose one partner to doing all the work.”

Septoria activity from the combination was as good as any other SDHI fungicide, and a step forward compared with the two best triazole fungicides, epoxiconazole and prothioconazole, he claimed.

But it was with rust, and yellow rust in particular, where he felt the product had an edge over its competitors in trials, although rival new SDHI product had only been tested using Syngenta-produced formulations rather than those which will be sold commercially.

Yellow rust could still be a problem this season, even after the cold December, his colleague Stephen Williams suggested. “Last year, after a cold winter we still saw it as a problem in some areas and in untreated trials.”

The isopyrazam + epoxiconazole combination had out-performed the current rust standard of triazole + pyraclostrobin significantly in high-pressure yellow rust trials situations, he noted, with yield increases of nearly 0.9t/ha over the strob mix.

A similar trial in 2010 had seen yield responses in the same range over Opus + Amistar, he added.

There was a degree of rate flexibility with the product against rusts, he said. “If you can guarantee the only diseases in the crop are rusts then you do have good flexibility.”

But that wasn’t particularly likely with virtually all crops needing protection from septoria, against which there was a significant drop-off in control at half dose. “You get the benefits of the new chemistry when using a full or at least a three-quarter dose.”

That was demonstrated in trials at ADAS Rosemaund where half and full rates of isopyrazam were added to epoxiconazole, along with plots with just the triazole fungicide.

Disease control was similar between the half and full rates, but there was a clear 0.75-1t/ha increase in yields from using the full rate of isopyrazam.

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