Tips for western growers for a busy April

Crop Progress

Crop growth always looks variable, but this year that’s obviously even more the case. Early planted wheats generally look pretty good, but the cold winds in early March sent other crops backwards, and at that point a lot of crops looked hungry for nutrition.

Some growers managed to get some early fertiliser on barley, some wheat crops and oilseed rape, but travelling conditions prohibited quite a lot at the beginning of the month.

Hopefully in the second half of March travelling conditions will have eased allowing growers to apply both fertilisers and weed control in wheat. Obviously, where either of those jobs haven’t happened then they will be top priority immediately in April.

Gareth’s agronomy tips for April

1. Ignore juvenile yellow rust ratings

It’s shaping up to be a yellow rust season in wheat, at least initially, after the mild winter weather. There were already reports of yellow rust in the usual suspect susceptible varieties in early March.

With the exception of a few varieties with good juvenile and adult resistance, there will be infection risk in a lot of varieties, especially in later drilled crops, which seems to increase risk.

I wouldn’t put much emphasis on the difference between juvenile susceptibility and adult resistance, as it is difficult to know when the adult resistance will actually kick in. Yellow rust is relatively cheap to control, but needs to be started early – it becomes more difficult in crops where it is well-established by the time you spray and you often seem to be chasing it all season.

That would lead to a T0 spray of tebuconazole or a strobilurin fungicide, remembering the strobilurin must have a mix partner and cannot be used alone. Mildew could be another concern early on, again more in late drilled crops, and may need treating with a specific mildewicide in some cases.

Don’t worry too much about leaf layer for T0 – the timing ideally should be no more than three weeks before when you expect to apply your T1.

2. Dissect plants for T1 timing

T1 timing is always a challenge, but this year with the spread of drilling dates and growth in individual fields it’s going to be especially hard. That means it will be vital to dissect plants and work out which leaf is emerging.

Don’t assume that it will be leaf three emerging at GS32 – with late drilled crops it could “drop” a leaf and actually be leaf two, for example. Ignore nodal growth stages and assess by leaf emergence.

3. Treat disease, not yield potential

Many growers will be looking at thinner crops of wheat and have a mindset to reduce fungicides because yield potential has been compromised.

Of course, there has to be some element to that, but in reality treating the crop for disease rather than yield potential is important, because disease doesn’t care about yield potential.

There will also be more yield contribution in thinner crops from the lower leaves, which would suggest against cutting inputs too much early in the season.

Early sown crops are likely to have more Septoria and eyespot, while later drilled ones will be more at risk from mildew and yellow rust. Brown rust will come in if it is warm.

Ascra® (bixafen + prothioconazole + fluopyram) remains a really good broad spectrum product to cover all those diseases at T1, while if you’re worried about Septoria and think you need a bit more efficacy then our new offer Vimoy® (isoflucypram), which comes co-packed with a prothioconazole product such as Proline® (prothioconazole) is also an option.

Vimoy and the Iblon® range provides extra activity against key diseases including Septoria, yellow rust and eyespot, and also extra greening benefits.

4. Tiller retention vital for winter barley yield

Barley yield is all about grains / sqm, and therefore maximising tiller retention. Early infections of disease can easily cause the plant to abort a tiller.

There’s also more contribution to yield from keeping lower leaves green in winter barley than in wheat. Those elements combined make the T1 spray in winter barley the most important. Remember it should be applied at GS30/31 rather than GS32 for that impact on tiller retention.

We have two good choices as options: Ascra and Siltra (bixafen + prothioconazole). Both will do a good job against the whole range of barley diseases, but Ascra® will give you a little more activity against net blotch and Ramularia.

In general, I would use Ascra at T1 for its broad-spectrum activity, but if you’re worried about Ramularia, which is a later season disease, then you could use it at T2. You only have one spray of Ascra available to use in a winter barley crop.

The way to stop Ramularia from expressing is to minimise crop stress, so anything you can do using nutrition or keeping other diseases out will also lessen the likelihood of Ramularia.

5. Don’t wait too long for the first fungicide in spring barley

If you’ve managed to drill some spring barley, my two main tips for spring barley disease control would be, first, don’t wait too long for the first fungicide as the crop grows extremely quickly once it gets going.

If you wait until GS30/31 in spring barley it might be only a couple of weeks until awns emerging – so the first one should be applied while the crop is tillering.

My second tip is don’t leave too long an interval between sprays, although that seldom happens. But if net blotch infects the crop it can cycle rapidly and be difficult to control.

6. Jump the last hurdle in oilseed rape

If you’ve managed to get oilseed rape this far, and some it does look decent in the west, then don’t fall at the last hurdle.

Keeping oilseed rape greener for longer directly correlates to yield and oil content, and applying a fungicide during flowering can help with prolonging green leaf area in the absence of disease.

For example, we’ve seen good yield responses from using Aviator® (bixafen + prothioconazole) in the absence of Sclerotinia. Of course, controlling both Sclerotinia and light leaf spot is important during flowering, which Aviator will do. Target your spray as petals begin to fall to provide three weeks protection against Sclerotinia. If flowering lasts for longer than three weeks you may need to consider spraying again.

7. Early weed control for potatoes

As this is written it’s difficult to imagine any potatoes going in the ground soon, but hopefully by the time you read it things will have changed.

Early weed control – pre-emergence of the crop – is vital in potatoes with limited options post-emergence. Strong options for pre-em weed control include Emerger® (aclonifen) potentially in combination with Artist® (flufenacet + metribuzin) or Sencorex® Flow (metribuzin).

Emerger doesn’t have any varietal restrictions, although the metribuzin products obviously do, it isn’t affected as much by dry conditions, and to get the best from it you should aim to produce well-formed ridges. If they’re not well-formed you might not get good coverage, which can let weeds through.

Acknowledgements

Ascra contains bixafen + prothioconazole + fluopyram. Vimoy containts isoflucypram. Proline contains prothioconazole. Iblon contains isoflucypram. Siltra contains bixafen + prothioconazole. Aviator contains bixafen + prothioconazole. Emerger contains aclonifen. Sencorex Flow contains metribuzin. Ascra, Vimoy, Proline, Siltra, Aviator, Emerger and Sencorex Flow are registered Trademarks of Bayer. All other brand names used are Trademarks of other manufacturers in which proprietary rights may exist.