Winter Barley Disease Management Could Be Trickier this Season
4 May 2021Like other crops, winter barley growth has been slow in the cold, dry weather and only in the more advanced areas like the Black Isle has much of it started to lift up and move into stem extension. Once we get a bit of warmth though growth and development will be rapid and many crops will be on the cusp of the important stem extension sprays. Disease levels have been reduced by the cold dry weather, but as ever the diseases have a few new tricks up their sleeves.
Rhynchosporium remains the major yield robber, but net blotch is becoming more of concern. One reason for this is that fewer seed treatments are available with good control of the disease, so some of what we are seeing crops now relates to seed borne infections. Certified seed helps reduce this risk rather than relying on chemistry, but if you have a crop intended for seed manage net blotch this year carefully. Creeping fungicide resistance is the other reason, though that net blotch is more problematic, with partial resistance to Strobilurins, SDHIs and Azoles now common. Relying on single actives is never a good idea and mixtures of fungicides applied together still work well. But we have seen an erosion in eradicant activity in trials and working protectantly is more of necessity this year.
The stem extension spray in barley is really key in retaining side tillers and potential grains sites which set the yield potential of barley early. This is different to wheat which will keep adding to yield, as long as there is sunshine and green leaf. Late green leaf is important in barley too, but fundamentally if it hasn’t set the potential grain sites at stem extension then there is nothing to fill later. This is why the T1 fungicides on the crop are pretty fundamental to later yield.
We no longer have Chlorothalonil to prop up programmes this year, and so you might need to increase rates of remaining chemistry to get the same level of disease protection as you were used to. The better news is that there is a good range of actives on barley so it is still possible to use effective SDHI, Strobilurin and Azoles in balanced mixes and to alternate products between timings. The main input will be at T1 around first node detectable, but a later spray at booting to ear emergence will help retain green leaf and manage ramularia plus any of the early disease than has persisted. The risk of ramularia in winter barley crops can be lower than in the spring crops, but much depends on the weather between now and booting. Like other disease, ramularia will not have enjoyed the cold dry weather. There is a link between ramularia risk and the cumulative temperature and moisture in a crop. Later sprays in winter barley that have done well in SRUC trials are the standards such as Siltra Xpro and Prothioconazole still retains reasonable ramularia efficacy, or the newer Revistar XE which is the leading product in ramularia efficacy trials. Check last application timings for malting and feed crops carefully though.
Mildew is also present in some winter barley crops – particularly in advanced areas. Previous experience with mildew is key to how you manage it. In areas where it tends to linger but not catch fire, then normal Prothioconazole based programmes will probably contain it. But in areas like the Black Isle where mildew flourishes, a specific mildewicide like Cyflamid will be needed . The multisite Folpet can add to winter barley programmes. It may help boost control in some situations but its efficacy has been erratic in winter barley trials.
Like other crops, winter barley growth has been slow in the cold, dry weather and only in the more advanced areas like the Black Isle has much of it started to lift up and move into stem extension. Once we get a bit of warmth though, growth and development will be rapid and many crops will be on the cusp of the important stem extension sprays.
Fiona Burnett (SRUC) for the Farm Advisory Service
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