South: Warmer conditions help late-drilled spring crops

Spring has finally sprung and crop walking in snow and hail is but a (fortnights) distant memory. Summer vegetable planting is well underway and first lifted new potatoes are doing well.

Challenging conditions resulted in some spring cereals and beans going in very late, but sunshine and warming soils with plenty of moisture helped establishment. Levels of barley yellow dwarf virus visible in winter cereals have made an early pass through the spring crops a given this season, with some manganese and magnesium accompanying the insecticide to assist early growth. There’s some evidence that adding zinc to the usual nutrients can help winter crops with patches of BYDV mitigate the effects, to an extent.

The cold end to April meant insect pest populations were slow to build. Pollen beetle was no issue in oilseed rape and I’m just beginning to see the odd seed weevil, so will consider an insecticide if thresholds are reached as flowering ends.

Pea and bean weevil has needed early control on slow growing spring crops to reduce numbers before eggs were laid. Winter beans are showing active rust, the start of downy mildew and a little chocolate spot. Wizard seems to be  a cleaner variety in my area. First fungicide spray will be cyproconazole plus chlorothalonil, with azoxystrobin added to improve rust control.

Yellow rust in wheat is becoming increasingly obvious where rates or timings of T0/T1 fungicides were compromised. Those who cut back too far will, I fear, see chickens coming home to roost over the next few weeks. Resistance ratings are being challenged, possibly by the recently reported Kranich race (a newly identified  pathotype) or by one of the new isolates of the Warrior strain. Seedling susceptibility is long gone – if you’re seeing it now on varieties rated 8 or higher send leaf samples to UKCPVS ( ).

Septoria and brown rust levels are also high – T2’s are imminent and based around an SDHI (fluxapyroxad) plus a high rate of triazole, a strobilurin and chlorothalonil. If you are firefighting yellow rust, the addition of spiroxamine to the mix may help, and be aware that chlorothalonil can reduce the eradicant activity of triazoles and some SDHI formulations. Crucially – ensure you hit the target. Flag leaf must be protected, regardless of how late you were with your T1. The gap between T1 and T2 should be a maximum 21 Days.

Last year was a very low disease season and, even where crops look well at the start of May, symptoms rarely become fully apparent until June in untreated trial plots.

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