How to manage backward cereal crops through April

Keep monitoring for weeds in ‘clean’ fields

Most growers, despite the horrific autumn which has left crops backward and patchy in many fields, did manage to apply residual herbicides, and, generally speaking, they have worked pretty effectively.

We’ve even escaped the same level of damage seen 12 months previously, even when some of the stronger actives have been used at a less-than-ideal timing post-emergence.

That’s meant we do at least currently have some clean fields, which didn’t need immediate action with a mesosulfuron-based product.

The watching brief should continue into April though, as these fields were generally drilled into cloddy seedbeds and still have a lot of soil showing. With some growers opting to roll to consolidate rooting, it’s quite possible that there could be a late flush of weeds – either grass or broadleaf weeds.

If that happens, make sure you read the label of the product you are using carefully as latest time of application restrictions begin to impact on choice. For example, the metribuzin-containing residual herbicides like Alternator® Met, which have still had a place in March, cannot be used past GS25 of the crop; some of the post-emergence choices have cut offs around GS30-32, while Atlantis® OD can be used up to flag leaf – although that’s definitely not a recommendation.

Rust the major concern at T0

There is a little bit of yellow rust already in Extase and Zyatt especially, but less so in Skyfall. The one or two fields that were September drilled have a lot of Septoria as lower leaves haven’t died off over winter, but generally there’s very little in later drilled crops.

I suspect, given the number of calls I’ve had on this topic, that many growers will not be taking a risk on missing a T0 if they can help it – upgrading to tebuconazole plus a strobilurin after seeing how difficult brown rust is to control once it gets going.

If you look at the Recommended List most varieties are below a 6.0 for brown rust resistance, which is a concern given the amount of inoculum from last year’s epidemic, although the trade-off is it was not as warm during the latter part of winter.

Yellow rust is perhaps the greater concern as research would suggest that later drilled crops are more susceptible.

Those risks will drive most to want to spray a T0 fungicide this season.

How to tackle T1 fungicides in later drilled crops

I’d usually suggest national T1 spraying day coincides around 25 April – but this year given the lateness of crops I think it might be a few days after this year.

In this region I suspect many crops will fall into the “value” rather than the premium camp. By that I mean Ascra® Xpro® or Revystar®, and even if there is no risk of brown rust, Elatus® Era. Vimoy® plus a partner will feature for some because of its rust and Septoria strength over the other common T1 options, particularly in varieties or regions with more of a brown rust risk.

It will also depend on what happens at T0 – if they are applied and there’s not too big a gap and there’s no active rust, then we have very little to fear from a 1.0 L/ha of Ascra® Xpro®, which is proving very popular thanks to good economics on the product. I cannot see many later drilled crops needing much more than that.

We also have a new option in Plaxium®. It commands a premium price over Ascra® Xpro® at the 1.2 L/ha dose, which delivers 50 g/ha of isoflucypram. It might be an option in those few early drilled crops, but the lack of higher Septoria levels probably means it could fit at T2 better this year in this region.

If you have a brown rust risk at T2 and don’t have Septoria levels that need a Miravis® Plus or Univoq® then Plaxium® fits nicely at T2 after an Ascra® Xpro® T1. It covers all the bases well, and compared with some other T2 products it is less expensive and you won’t need to add an additional product for rust control.

Spending at T2 doesn’t change what you need to do at T1 in winter barley

There’s nothing like the normal area of winter barley this year for a few reasons – first the commodity price, secondly the need for an early entry into oilseed rape is less important with the demise of that crop’s area, and finally the rain in the normal winter barley drilling window meant a lot of planned crops could not be successfully drilled.

There’s quite a lot of net blotch in barley crops that were drilled, which is something to take account of at T1. In the rush to possibly use a very good new, but expensive, product at T2 in barley, there’s a lot of discussion around making T1 as cheap as possible because the barley grain price is less than inspiring currently.

But that risks forgetting the importance of T1 in winter barley – you cannot lose tillers or let the crop carry high levels of infections into flag leaf and ear emergence or it will affect yield.

So even if you are thinking about using Miravis® Plus at T2, and it is technically a strong option, you cannot let that effect what you do at T1 and will need to spend a little more on your programme.

And in my opinion Ascra® Xpro® is the best T1 you can apply. I’m a big fan having listened to our fungicide resistance expert talking about net blotch and Ramularia of having mixed modes of action across the programme, which could also include a strobilurin fungicide at either or both timings.

Oilseed rape

Despite the annihilation by pigeons, I’m hopeful oilseed rape will recover as many crops do have half-decent root structures, despite the wet.

Where crops do still have leaves remaining there are some reasonable levels of light leaf spot – hopefully that has been taken into account with a stem extension spray.

Once crops start flowering, it will be a good idea to use a product with a mixed mode of action, such as Aviator® Xpro® as technically it is the strongest option against light leaf spot, with its two modes of action. It will also cover the risk from Sclerotinia, the traditional reason for applying a flowering spray – although one could argue that light leaf spot is now the major reason for this application.

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Alternator® Met contains diflufenican, flufenacet and metribuzin. Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Aviator®Xpro® contains bixafen and prothioconazole. Elatus® Era contains benzovindiflupyr and prothioconazole. Miravis® Plus contains pydiflumetofen. Plaxium® contains isoflucypram, fluopyram and prothioconazole. Revystar® XE contains fluxapyroxad and mefentrifluconazole. Univoq® contains fenpicoxamid and prothioconazole. Vimoy® contains isoflucypram.

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