While overall disease pressure may be lower after the driest March in 60 years, and a dry April, short-term stresses and nutrient deficiencies caused by the lack of rain could increase the risk of certain diseases in barley.
This is the warning of Hutchinsons’ head of integrated crop management, David Howard, who says: “Crops remain variable across the UK, largely based on the state of soils at drilling, and the weather received over winter.
“Prolonged cool nights and dry weather have extended early growth stages, but with daytime temperatures spiking into the high teens, some barley crops are now moving rapidly towards T1.”
He adds that plant defences may be lower due to the current conditions, so growers need to assess disease risks in individual crops.
A variable picture
Reports from the southwest suggest that ramularia symptoms are being seen earlier, especially on light soils or in crops with significant stress.
“Mildew is also widespread, especially in crops stressed by poor weather, high nitrogen levels, or dry weather.”
However, net blotch and rhynchosporium pressure has been lower than in previous years, while cooler temperatures so far have subdued brown rust.
“Barley grows rapidly during this time, adding biomass quickly and relying heavily on lower leaves, which contribute significantly to green area index. Barley’s lower leaves are larger and play a more prominent role in photosynthesis alongside stems and ears, unlike wheat, where upper leaves dominate yield contribution.
“Retention of tillers is also essential in barley to maintain yield potential, therefore getting disease control right and reducing plant stress at this early timing is key.”
Combining SDHI and azole products can reportedly provide robust activity against multiple diseases, however David notes that growers should be mixing multiple modes of actions and alternative actions to mitigate resistance.
Net blotch strains resistant to SDHIs and strobilurins are becoming more common, for example, although there is differential control between strobilurins, with pyraclostrobin being less affected than others, he notes.
For ramularia, the most active product is now pydiflumetofen, so should be considered where significant disease is already confirmed, he advises. If not, the product is best kept for T2, where ramularia is more commonly seen. Another option in high-pressure situations is mefentrifluconazole, and he also suggests adding folpet, or a biostimulant such as Scyon, for consistent protection.
Where mildew needs controlling, cyflufenamid is effective, but he reminds growers to avoid consecutive sprays of cyflufenamid to prevent resistance. “For moderate cases, consider prothioconazole-based products.”
Benzovindiflupyr, tebuconazole and strobilurins such as pyraclostrobin, are all options for brown rust, but tailor choices to specific situations and the need for curative control and/or lasting protection, he says.
He notes that if T0 applications were recently applied, growers have the flexibility to adapt the T1 timing to GS 31/32, but if no T0 was applied, the earlier GS 30/31 timing will be essential and higher dose rates may be needed to improve curativity where required.