South: Disease and rooting dangers in wheat

Steady growth in a spring yet to show any rapid warming and imposing no moisture stress whatsoever means our winter crops are generally well structured and clean, if a little patchy in places.

However, it’s important to keep reminding ourselves that, with more than enough moisture in the ground and regular additions from above, we could be sitting on a time bomb when temperatures and crop growth really pick-up.

For wheats, the ticking is two-fold – foliar disease and rooting. Apart from one field of Leeds full of active yellow rust through lack of a T0, septoria is our key concern. Thankfully, there’s been little obvious disease movement up the crops so far. And our T0s – the most northern of which only went on a week ago with the slow emergence of Leaf 4 – should be doing a good job holding back latent infections.

So, with Leaf 3 already a good 40% emerged further south, many crops could be facing a T0 to T1 gap of little more than two weeks. Which means our timings have to be guided by leaf emergence, not spray interval, and our treatments must be sufficiently robust if we are to adequately maintain our septoria defences.

That’s why our T1s will definitely include an SDHI supported by a azole – in most cases prothioconazole for its extra stem-based disease activity. Even last season, Agrii trials recorded a 0.25t/ha response to our preferred SDHI, underlining its economic value.

We’ll also be taking a robust plant growth regulator (PGR) approach at T1 to protect ourselves against major root lodging dangers. The wet winter has left many crops lacking in the root department and no lack of soil moisture means the potential for some seriously big canopies. Again, therefore, we’d rather be safe than sorry; especially with root lodging such a key issue these days.

On the oilseed rape front, light leaf spot is our biggest concern. A slow creep into flowering means some nice, compact, very well-branched crops with just the canopy architecture we want. As well as helping to keep them this way, our late March/early April stem extension sprays are continuing to hold the disease well.

But, knowing how much inoculum is about, we’ll be including a decent level of prothioconazole in our flowering spray for late light leaf spot protection – in most cases alongside the fluopyram we favour for its combination of sclerotinia and alternaria activity.

With such a late start, oilseed  rape flowering isn’t shaping-up to be overly long this season. So, with a later-than-normal stem extension spray and a low early sclerotinia forecast, a single mid-flowering fungicide may well be enough in most cases. Like the generally low level of pollen beetle spraying we’ve needed, this would be most welcome.

Despite a challenging season for spring drilling, most of our spring barley’s are up and growing away well. For the first time for years, though, we’ve experienced some notable slug problems – mainly after cover crops that hadn’t died back before drilling. A clear future watch-out here.

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