Wheat growers are being urged to look at fungicide actives rather than products to control multiple diseases, and this has been highlighted by the early virulent attacks of brown rust this spring.

Brown rust has infected wheat crops very early this season due to a mild wet winter followed by the warmest May on record, as the disease spreads quickly in wet and warm conditions.

Aoife O’Driscoll, crop protection specialist at consultant Niab, says with inoculum overwintering and early fungicide sprays being missed due to the wet spring weather, favourable weather conditions have allowed the disease to spread rapidly.

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In reaction, she is now looking to focus growers’ attention on specific actives rather than broad-spectrum products to control infections, and in the case of brown rust the disease can cycle quickly in five or six days during warm weather.

“We are encouraging growers to think about actives rather than products, and then look at the strengths and weaknesses of each active,” she tells Farmers Weekly.

Aoife suggests growers look carefully at which actives have an effect on each disease, such as brown and yellow rusts and also septoria, while pointing out there is a new winter wheat variety which is the first to show both juvenile and adult brown rust resistance.

Some growers struggled to distinguish brown rust and yellow rust in the early spring, as the last time brown rust appeared so early was 2007. However, climate change could make mild winters and warm wet springs more prevalent.

Many failed to get a T0 spray applied in late March, but if conditions are favourable and brown rust is a threat, Aoife suggests a spray of a strobilurin would be a good choice, or tebuconazole if yellow rust is the bigger threat.

She points out that for T1 and T2 timings, if brown rust is a threat then growers should look to choose an SDHI with the best possible activity against the disease, such as Solatenol or Iblon, supported by an appropriate azole.

If other products are used, such as Adepidyn or Inatreq, then extra rust control may be needed in a high disease season.

The T3 ear spray is advised to be based around a strobilurin and tebuconazole, with prothioconazole added for fusarium. She suggests strobilurins are best used early and late in the season, so at T0 and T3.

Variety selection is being made more complicated by diseases popping up nationwide rather than rusts in the East and septoria in the West, while drilling date is always a compromise, with late drilling good to limit septoria but possibly encouraging rusts.

Autumn drilling

A good compromise could be drilling in the second half of October, while she points out that the variety Goldfinch looks interesting as a new variety as it has both juvenile and adult brown rust resistance

Lee Bennett, managing director at the variety’s breeder, RAGT, says this wheat variety could be especially important when the threat of brown rust is severe.

“Goldfinch is the cleanest wheat variety that farmers can grow,” he says.

The Group 2 milling variety comes up for possible inclusion in the AHDB Recommended List (RL) later this year, and Lee adds that the variety has resistance scores of 9 for yellow and brown rusts, 8 for mildew and 7 for septoria, in a 1-9 scoring range where 9 shows good resistance and 1 is very susceptible.

The variety, like all recent RAGT products, has resistance to barley yellow dwarf virus and also to orange wheat blossom midge, like Wolverine and Grouse.

“We’ve not seen brown rust in May for a long time, and it has largely been seen as a hot weather disease that comes into crops in late June and early July,” he says.

Many varieties have moderate resistance scores for brown rust ranging from 5 to 7, such as the popular varieties Dawsum (7), Extase (6) and Champion (5), while Skyfall stands out as the only 9 on the RL and Crusoe has a lowly 3.

© MAG/Richard Allison

Agronomists’ views

One agronomist who is used to being on the lookout for brown rust is Jim Woodward at advisory group Farmacy, as he looks after a big area of the susceptible milling variety Crusoe in the brown rust hot-spot of north Essex and south Suffolk.

He says T0s were not often used for Crusoe as it has good resistance to yellow rust (8), but this season his crops generally had a strobilurin/tebuconazole mix in late March to control early brown rust.

“We had to think about brown rust a lot earlier this season,” he says.

His T1s were based around Iblon with prothioconazole, and his T2 had Adepidyn with prothioconazole again added, but this time with tebuconazole included to bolster Adepidyn’s only moderate control of brown rust.

His T3 head sprays are usually based around a strobilurin plus prothioconazole, but this season tebuconazole was added to the mix to bolster brown rust control.

Further north, independent agronomist Patrick Stephenson says he is near the cusp for the severity of brown rust, as he has kept the disease under control in his area of North Yorkshire, while south of York the disease is more virulent and difficult to control.

The disease was later to arrive in North Yorkshire than further south, so Patrick was keen to bolster his SHDI-azole treatments at T2 with a strobilurin or tebuconazole.

His T3s are important as he looks to keep his crop green before a late harvest in northern England, and he has looked to load these for brown rust control. This can mean a strobilurin at T3 or even Solatenol, if the limit of two SDHIs in a season has not been met.