JUST AS in rugby football, the so called north south divide is very much in evidence in cereal crops this season – and we Scots seem to be losing out.

It is normally the south that frets over foliar disease early on and while frosts have checked septoria and yellow rust further south, that hasn’t happened here. Hopefully, we are not heading for another 2012, but alarm bells are gently ringing for Scottish agronomists.

That year, septoria took hold after a mild winter combined with showery spring conditions impaired T0 and T1 sprays, costing Scottish growers dearly. Should that happen, the arrival of new SDHI chemistry in the form of Ascra Xpro (prothioconazole + bixafen + fluopyram) and Elatus Era (prothioconazole + benzovindiflupyr) will help, but vigilance is needed with early season control too.

Scottish Agronomy director, Andrew Gilchrist, said the situation is not as bad as then for the same time of the season, but is preparing for a heightened risk this season.

“We’ve had a dry autumn and winter, but not the drought conditions of further south. There’s been enough rainfall to ensure most wheat crops established well, but also to keep septoria ticking over," he pointed out.

"The threat isn’t just one of further rainsplash if the weather stays favourable, but leaf transfer too. We have some very lush crops with plenty of biomass right now and it is a similar position with winter barley, promising potential but possibly greater disease concerns,” he cautioned.

Along with septoria, which is visible on lower leaves in wheat, mildew is also a concern. Mr Gilchrist says the ingredients are there. “Mild conditions and forward crops, some susceptible varieties. It’s all there!”

A double whammy is delivered by Scottish variety choices and drilling dates. “Typically, the varieties that are proving popular range from four to a low six for septoria. To compound matters, many crops are drilled in September, while further south that doesn’t happen as growers delay drilling to battle black-grass.”

Bayer’s Neil Thomson agreed and pointed to just how susceptible some popular varieties are. “Leeds is below five for septoria and just three for mildew. Prothioconazole is a good mildew product but a morpholine might be needed at T0 or T1,” he told The SF.

A concern for him is T0 sprays being pulled forward – something he urged growers to avoid if possible. “The majority of yield is generated from the top three leaves. If T0 sprays are forward, then it is likely that T1s could be too, exposing leaf three to infection," he argued.

"I would rather growers hold off T0 sprays and clean up any rust infection with a rust active azole or strob with CTL to hold septoria pressure. Cherokee (propiconazole + cyproconazole + chlorothalonil) would be an appropriate choice.”

If T0 sprays are forward, Mr Thomson endorsed a SDHI mix at T1. “Azoles have little curative activity, so only an SDHI will provide any kick back. A product like Aviator235Xpro (prothioconazole + bixafen) will provide septoria and stem based activity.”

Mr Gilchrist agreed and added that SDHIs are not a ‘default’ position, but stressed the importance of timing. “With the loss of azole curativity, it means that the T1 window has narrowed. A few years back you might have got away with a slight timing error but you can’t any longer.

"The additional curative activity of an SDHI will undoubtedly help in such situations but, ideally, they should be used as protectants. We don’t want to be going down the curative route – it will only break them.”

The ‘default’ position is the T2 and he welcomed the arrival of new chemistry. Having had Ascra and Elatus in trials his hunch is that they may offer some additional potency compared with existing products.

Elatus looks a good yellow rust option, while Ascra is particularly good against septoria. “Ascra’s got two classes of SDHI, our best septoria azole and you can add in CTL. In terms of preventing resistance, we can’t be doing much more either.

“Both performed well last season, but with reduced disease pressure maybe we didn’t see them at their best. The differences in many of our plots were quite small. If disease pressure remains high, then perhaps those differences will be more marked this season,” added Mr Gilchrist.

Apart from the most curative situations Mr Gilchrist would use both with CTL, which he sees being used at T0, T1 and T2. “It gives the same level of protection as a robust dose of a primary azole and provides another mode of action to protect SDHI and azoles.”

Also, Mr Thomson is wary of cutting rates, which some might find tempting if disease pressure falls due to dry cool conditions. “We need azoles and SDHIs to be protecting each other, so rate is vital and if the weather turns then crops could be left inadequately protected. Disease control equates to just 10% of winter wheat production costs.”