Kent grower Richard Budd saw a yield jump of 1t/ha from his winter wheat crop by using a new fungicide, which is likely to also help fight against disease resistance.

In a farm-scale trial, the new azole fungicide kept his wheat greener for longer throughout July and so out-yielded his farm standard fungicide programme.

See also: Cliff edge of fungicide resistance faced by wheat growers

The new product, Revysol from agrochemicals giant BASF, cleaned up septoria disease that had come through the winter when applied at the T1 stage in April.

A further treatment at the T2 flag leaf stage was also applied and Mr Budd’s crop of the milling variety Lili gave a yield of almost 15t/ha on his heavy land farm.

“We see huge benefits from the product at T1 and this gives us the option of a less expensive option at T2,” he told a briefing to launch the new fungicide.

New for this spring

A new azole-SDHI product, called Revystar, will be available this spring containing the new azole Revysol with Xemium, the same SDHI used in Adexar and Librax. Revysol will not be available as a straight product to protect against disease resistance building up.

The new azole shows the same activity against septoria as older azoles like prothioconazole and epoxiconazole, before their activity against the disease declined.

In a 14ha trial field, Mr Budd used a farm standard T0 spray then compared a T1 and T2 of Revysol with a T1 of Ascra and a T2 of Elatus Era, followed by a T3 head spray of Firefly and Toledo across the whole field.

Higher yield

The farm standard Ascra-Elatus programme on the first wheat crop gave a yield of 13.98t/ha while the Revysol-treated area stayed greener for longer and added a further 0.99t/ha to yield, or 14.97t/ha.

Mr Budd was first encouraged to use the new product at T1 due to results from the septoria-favourable climate of Ireland where under high disease pressure wheat crops had stayed green longer.

On his farm there was no obvious difference across the trial in a generally low-disease spring and summer 2019, but from late June onwards the new azole showed good curative septoria activity and kept the crop greener for longer.

“Going forward the answer will not always come out of a can, but when it does, then we are very grateful,” he added.

He farms with his father some 1,000ha of combinable crop at Stevens Farm in Hawkhurst on heavy Weald clay, and won the 2019 Yield Enhancement Network with his oilseed rape crop in a competition run by crop consultant Adas. His crop of 7.19t/ha was an unofficial world record yield.

Phenomenal control

Julie Smith, principal crop pathology researcher at Adas, said the new azole showed “phenomenal” curative control against septoria strains, which were insensitive to other azoles, such as prothioconazole.

“Revysol is outperforming prothioconazole at every timing for septoria control for 15 days either side of the T2 fungicide timing,” she said.

This gave about a 1.2t/ha yield response when both treatments were applied at the flag leaf stage in a cross-site analysis by Adas.

“It doesn’t matter how severe the septoria is, what shifting of resistance there is or which variety is grown, there is a benefit from Revysol at the T2 timing,” she added.

Endocrine disruptors

Rosie Bryson, senior principal scientist for fungicide development at BASF, says Revysol minimises the impact of the enzyme target for the mammalian endocrine system. This mean that it is unlikely to be classed as an endocrine disruptor, which is threatening the use of older azoles like epoxiconazole.

She also pointed out that the structural flexibility of the Revysol molecule allows its “flexible hook” to bind securely to the attacking fungal enzyme.

Steve Dennis, head of business development at the agrochemicals group, added that Revysol is five times better at binding to the fungus site than the second best azole-binder epoxiconazole.

He pointed out the rapid uptake of Revysol by plants gives good curative action against diseases such as septoria while the fungicide’s slow movement through plant leaves gives it good persistence.

Lower dose

The good activity of this azole allows the combined Revystar to have a 24% lower dose of SDHI than in Adexar as the new combination does not rely heavily on the SDHI as it is combined with a strong azole.

“We are using less SDHI to get better control so we are no longer relying on a vulnerable class of chemistry,” said Mr Dennis.

On ramularia disease in barley, where the only good control comes for chlorothalonil which is set to be banned in May 2020, he added that Revysol is the second best active for the disease after chlorothalonil.

The cost of Revystar is not being revealed, but after spending €250m to develop the Revysol molecule, the company says there will be an “innovation premium”.