Challenges and decisions for cereal growers ahead of key flag leaf spray applications
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Corteva Agriscience is advising cereal growers to use the latest fungicide chemistry to help them navigate the complications they face ahead of flag leaf spray applications.
Sprays targeted at keeping septoria and rusts off the flag leaf typically start from the middle of May. But drilling date, variety choice, and weather conditions have all contributed to a huge divergence in growth stages and disease prevalence.
Corteva’s Field Technical Manager, Craig Chisholm, said: “Comparing crops across the country, we are seeing wheat which is only just having its T1 spray while other farms are preparing their T2 mixes.
“This will have been influenced by drill dates and varieties, but regardless of their growth stage crops generally look very good and have strong potential. The challenge will be getting T2 sprays on at the right time when there is not a great degree of uniformity.”
Spring spray days have been at a premium with catchy weather leaving many unable to travel at the optimum time in order to carry out weed and disease control.
Some T0 applications were abandoned altogether, while T1 sprays took place where weather windows presented themselves. Craig said this is being reflected in disease pressure which is building in line with May’s climbing temperatures.
“There is plenty of septoria in the base of the crops in the trials we have been looking at and the warm, wet weather will contribute to infection further up the plant,” he said.
“Yellow rust has not been visible in many varieties until now – but is perhaps more evident in the south and west of England at the moment.”
Frontier’s Crop Production Technical Lead, Paul Fogg, said: “Septoria has not reached epidemic levels, but there is certainly more present than we’ve seen for a long time, probably driven by early drilling and temperatures over the winter.
“But autumn crops are looking good. Those who managed to execute their programmes this spring are definitely in the driving seat.”
To help tackle the season’s challenges, Craig advises growers to use fungicide chemistry with both protectant and curative qualities.
He said: “Getting the timing of T2 sprays perfect is going to be a real challenge this year – it’s going to be easy to be a bit early or a bit late, so you need a fungicide that will stop disease taking hold, or act on any diseases that are present in the plant.
“UnivoqTM has proven its ability to deliver curative and preventative persistence against yield-robbing diseases, perhaps most notably in 2021 when a wet spring created similar circumstances to what we are facing today.”
Predominantly used at the T2 fungicide timing – growth stage 39 – to elicit the greatest possible yield response, Univoq helps contain latent disease and protect the crop for the following four-to-six weeks.
Paul added: “The season seems to be playing into the hands of the Inatreq molecule because of its disease control and longevity – it’s a long way to harvest so growers want something that’s going to stay the course.
“There will be decisions to be made around rates; 1.25l/ha is going to be a good starting point for many, but there are high-pressure situations already, and for those whose crops aren’t ready for a flag leaf spray yet, there is still time for pressure to build in this wet and warm weather.”
A standard application of Univoq at the T2 timing is 1.25l/ha, but rates can be adjusted up to 1.5l/ha or down to 1.1l/ha depending on variety and disease prevalence.
Corteva advises that the 1.5l/ha rate should be targeted where disease pressure is already high, the T1 to T2 gap may have become extended, and where greater persistence of control is required because of ongoing rainfall causing frequent infection events.
Trials in 2021 indicated that, under these circumstances, increasing the rate from 1.25l/ha to 1.5l/ha gave a 0.15t/ha yield benefit worth £33/ha at current wheat values.
Corteva has urged growers to follow its best practice application advice when applying products containing Inatreq active.
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