After a late start to the season, spring barley crops are growing rapidly. Disease management needs in a shortened season can be hard to judge. Late season green leaf retention is important to yield and quality, particularly in a compressed season and there has been a lot of concern over fungicide resistance in ramularia where, in the absence of very robust varietal resistance in any of our current spring barley varieties, we are reliant on the multisite chlorothalonil to protect crops at risk of a rapid loss of green leaf area to ramularia this season.
Although it may seem like a done deal with ramularia, walking crops this season and watching for spotting symptoms is important so that a picture of on-farm ramularia risk can be built up for future planning. Accurate identification is important in this – we get a lot of spots coming into the SRUC crop clinic where ramularia is wrongly blamed. Commonly ramularia appears after flowering so it is very unusual for it to appear before this. Abiotic stress and net blotch can also cause spots on the upper leaves so the easiest way to indentify ramularia is that it goes right through the leaf. If you turn the leaf over and see the same lesions on the back that is a good indicator of ramularia. Its rectangular shape, restricted by the veins, and the yellow ring around the reddish coloured spots are also typical.
Ramularia is now widely resistant to SDHI, azole and strobilurin fungicides, hence the reliance on chlorothalonil. But it is important to remember that these fungicides are still effective on other key barley diseases – rhynchosporium and net blotch. Protecting against these diseases is also important, particularly on varieties with lower disease resistance ratings such as Concerto, or on wetter sites.
Maintaining yield in spring barley is dependent on retaining as many tillers and grain sites as possible at the end of tillering / very beginning of stem extension, which is termed T1 in spring barley. In a very rapid season like this one where crops are still clean then the risk of disease ingress is reduced but for crops aimed at a quality malting market then protecting at T1 against the full basket of diseases can be important because if disease gets in before the T2 sprays, applied at booting to awns just peeping, then eradication will be hard. In addition, a heavy disease burden from other diseases and the use of harsher eradicant chemistry may stress the crop which makes ramularia symptoms worse. But inputs at T1 can probably be scaled back this season to reflect the rapid growth and reduced risk. The booting spray should be the last of the season – there is no additional yield or quality benefit to using head sprays (T3s) in spring barley.
Fiona Burnett (SRUC) for the Farm Advisory Service
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