There are a few really key changes to disease management options in wheat for this year, and layered onto this are of course the vagaries of this season’s weather. The cold dry weather means that wheat crops have rather stalled in their development and stayed low to the ground, waiting to move in to stem extension. Disease levels have visually dropped as older leaves wither away but we all know that a spot of warmth and rain will let it tick up again. But it is certainly helpful in the crops that did not get early T0 sprays – cold dry weather is better than any fungicide!
This is the first season we will go into with no Chlorothalonil. That is really important to remember as it propped up wheat programmes to a significant degree in the last few seasons. The alternative multisite Folpet is about 50% as effective. That is not nothing so with a few key adjustments we can cope with the change. It does mean that low input T1 options based on Azole and a multisite (Folpet) will probably be less widespread this year than when we could use Azole plus Chlorothaloinil and so the Azole + multisite option this year is only suited to the lowest risk situations i.e. resistant varieties, late sown and already very clean. For the most part, adjusting programmes to include an Azole and SDHI component plus Folpet will be a sensible starting point. You can then moderate the dose to suit the risk on a crop by crop, field by field basis. This lets you cover Septoria well but also factor in eyespot and yellow rust risks.
The other change for this year is the loss of Epoxiconazole. This Azole, once so common in wheat programmes, can still be used until October if it is already on farm but cannot be sold or bought. So two key messages – if you still have it, try and use it up where you can to avoid later disposal costs. That includes the Epoxiconazole mixture products like Tracker and Nebula, previously used for eyespot management.
Good news in terms of new products in that we have the approval of the new mode of action Intraeq in the form of Univoq (a mix with Prothioconazole) to look forward to. This brings a genuinely new family of chemistry to wheat programmes. It is a flag leaf option for this year and in future seasons the chance to alternate between SDHIs and Univoq over the main timings is very positive.
Resistance risk remains an issue and it is really key with a diminishing chemical armoury that we steward and use sensibly what we do have. Flag leaf sprays are a key and highly responsive timing and worth getting right, and they are a good position for the best of the SDHI and Azole chemistry available such as Ascra Xpro and Revystar XE and now of course Univoq. Adding in the multisite Folpet will boost efficacy and help to protect the other chemistry. Try and plan programmes out in advance strategically so that you don’t find you have run out of rope when it comes to maximum application numbers or dose of individual components, and then moderate dose if the weather is very dry and disease risk reduced. Adjust to sow date and varietal risks too. At the moment early sown crops are the ones where most of the disease is sitting and drilling date is the main driver, but we usually see the benefits of varietal resistance kicking in from this point onwards.
Where yellow rust is an issue, Azoles remain very key with some added benefit from the SDHI component. Adding in Strobilurin can boost rust efficacy. And some SDHI and Azole mixes have particular strengths in yellow rust – an example being Elatus Era.
Fiona Burnett (SRUC) for the Farm Advisory Service
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