South: Planning for increased disease pressure this spring

The cold spell put paid to plenty of cereal leaf and has definitely helped reduce the disease reservoir. Even so, yellow and brown rusts are still easy to find in many of our wheat crops, septoria is not just confined to the lower leaves, and mildew continues to be obvious.

Another dry spring may relieve some yellow rust and septoria pressure, but it’s unlikely to do much to keep brown rust in check. Whatever the weather, the last thing we’ll be doing this season is skimping on our T0s. Especially not with such a large proportion of our national wheat acreage down to varieties with less than ideal rust resistance.

Robust rates of rust-active triazoles, with a mildewicide where necessary, will be the order of the day for most of our wheats. We won’t be tempted to go in too early, though. T1 timing here is invariably around 25 April  and we know a gap of more than four weeks from T0 leaves crops wide open to rust development.

We don’t want to be going in too early with our first plant growth regulator either. If we put it on before the end of tillering (GS29/30) all we’ll be doing is encouraging already thick crops to thicken-up further rather than keeping them stronger and shorter. So we’ll be holding our nerve and spraying at our normal T0 timing in the last week of March or the first week in April.

Speaking of nerve-holding, it has worked a treat with our oilseed rape blackgrass control this season. We held back on the propizamide until December when both temperatures and soil moisture deficits had dropped. And we’ve seen fantastic control. Which is just as well with the worryingly mixed autumn blackgrass control we’ve seen on the wheat side of the rotation.

The February chill has really done our oilseed rape some good. It’s amazing how well many crops have corrected. The cold hit them particularly hard because they’d already begun to grow away in the mild January.

There are still some over-thick crops around but that’s down to people using too much seed. Our crops are, for the most part, not excessive. Pigeons have only just started to flock-up and do some damage but it’s too late to be much of a problem, providing they’re kept moving. All-in-all, the rape is well-placed to respond to its canopy nitrogen which we will, as ever, be carefully matching to green area indicies and soil N-mins.

In most cases, our first OSR nitrogen will be going on in the coming week once spring barley drilling is completed. Those who got their primary cultivations done in the autumn are profiting from a wonderful frost tilth this season, allowing them to develop great seedbeds a good fortnight ahead of last year. In contrast, freshly cultivated spring cereal ground is certainly proving more of a challenge.

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