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Disease Management

Bayer Crop Science

Crop Doctor - Still plenty of potential to protect at T1

Article overview

With the T1 fungicide timing fast upon us, last week Bayer’s Crop Doctors embarked on their first tour of the season, visiting sites in North Yorkshire, Lincolnshire and Herefordshire to assess crop development and disease levels.

The very wet and relatively mild winter has inevitably provided conditions favourable to septoria at all sites. But with high levels of yellow rust in commercial crops, together with reports of eyespot and brown rust in some regions, the Crop Doctors were keen to get into the plots of current AHDB Recommended List and candidate varieties to form a nationwide picture of the disease challenges facing growers this season.

With a wide variation in crop development, there was also plenty of discussion around the importance of correctly identifying leaf 3 emergence to ensure that T1s are applied for optimal effect.

North – Cawood, North Yorkshire

Small plants and active yellow rust

It is a bitterly cold day in North Yorkshire and Fiona Burnett, professor of applied plant pathology at SRUC, is carefully stripping leaf layers away from the stem of a young wheat plant with fingers that are growing increasingly numb.

She will do this several more times in the next hour or so to determine the growth stage of this plant and others in a field of 35 winter wheat varieties at Bayer’s trials site at Cawood near Selby.

Prof Fiona Burnett, Arable Knowledge Lead, SRUC

Although there are discernible differences in development between the varieties in terms of their height and biomass, most have four leaves emerged on the main stem on this October 18-drilled, sandy clay loam site, although those on a slightly wetter area of the field are a little more backward, feeling the effects, no doubt, of having wet feet for most of the winter.

“I would say that generally, plants here seem smaller than we might normally expect at this time of year,” says Fiona. “They are still sitting quite low to the ground.”

A brief spell of dry weather allowed the team at Cawood to apply a T0 of 0.5 litres per hectare of Folicur (tebuconazole) on April 10 and disease levels are generally quite low, although septoria is present at low levels in almost all varieties.

Dipping into plots at random, Fiona notes that Graham is looking clean, KWS Dawsum has a little bit of septoria on its lowest leaves while a few rows down, Champion is sporting a few spots of yellow rust.

“I’ve seen worse septoria here at this point in the season in previous years, but it has been present in crops over the winter and levels are starting to climb, which is inevitable given it has been persistently wet,” says Fiona.

In search of some properly active yellow rust, she dives off into a plot of Zyatt, rated 3 for resistance to the disease, and isn’t disappointed.

“Yellow rust is plastered over leaf 6,” she says.

While brown rust has been reported in crops further south and west, it isn’t currently finding conditions at Cawood to its liking.

Eyespot is also absent at the site but is an important consideration at the T1 fungicide timing given that none of the top 10 winter wheat varieties for yield on the AHDB Recommended List have an eyespot rating above 6, says Bayer’s Tom Sowerby.

“Stem bases here actually look quite clean and that is a positive, but an October 18 drilling is not particularly early,” he says, referencing the increased eyespot risk with earlier drilling.

With T1 sprays approaching, correct identification of crop growth stage will be particularly important this year, given the wide variation seen in winter wheat development across regions, farms and even within fields as a result of the wet weather, says Fiona.

At Cawood Zyatt is the most forward, with leaf 3 just peeping out and is a good two weeks ahead of some of the later varieties on the site.

“The rule of thumb is that the T1 spray is applied at GS32, which is when leaf 3 is emerging,” says Fiona.

“But GS32 is something of a made up growth stage, where there are two distinct internodes visible, and you can measure two centimetres between them.

“However, some varieties are taller than others, in some years crops are shorter and basically, the crop doesn’t know that we’ve set this two centimetre rule.

“This year crops are short here and so the classic GS32 rule may not apply. Peeling back leaf layers and counting what leaves have emerged will be important and wait until leaf 3 is properly emerged before going in with the T1.”


Ascra contains prothioconazole, bixafen and fluopyram. Vimoy contains isoflucypram. Ascra, Iblon, and Vimoy are registered Trademarks of Bayer. All other brands listed may be Trademarks of other manufacturers and proprietary rights may exist. Use plant protection products safely. Always read the label and product information before use. Pay attention to the risk indications and follow the safety precautions on the label. For further information visit or call Bayer on 0808 1969522.

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