Growers who still have to complete T1 sprays are being advised to use no less than a three-quarter dose of a primary azole to protect against the growing threat of septoria.

For the week commencing 17 April, more than 23mm of rain was recorded at Bayer’s Callow trial site, and Bayer’s Gareth Bubb warns that septoria is abundant in many crops.

“Leaf 3 hasn’t the same yield-building properties as the flag leaf, but it can act as a source of inoculum for leaf 2 and the flag leaf. Where growers haven’t been able to get on yet then I would be urging them to use robust doses of prothioconazole or other septoria-active azole to increase curative activity,” he says.

It’s a similar picture at the company’s trials site in Cawood, North Yorkshire. Since 13 April, close to 50mm of rain has fallen. Site manager Sean MacGill warns that with plenty of T1 sprays still to go on, growers’ resources could be stretched.

“Many are struggling to get on with their T1 applications and with crops growing fast, T2 sprays will be imminent. Our advice in such situations is to try to stick with the GS39 timing, rather than extend spray intervals to a four-week gap from the T1. The flag leaf is the most yield responsive timing, and protection against septoria is vital.