Stay alert to Septoria, wheat growers urged

Stay alert to Septoria, wheat growers urged22 March 2021

Winter wheat growers are being urged to be aware of much higher levels of Septoria in crops this year compared with last season, most probably brought on by earlier drilling.

According to ProCam northern region technical manager, Nigel Scott, assessments at the company’s trials hub at The Stockbridge Technology Centre, Cawood in Yorkshire, have revealed active infections of Septoria tritici even in varieties with good resistance where these were drilled early.

Mr Scott says: “People have taken their eye off Septoria a bit. But we have to remember it’s the UK’s number one wheat disease.

“Significantly, it’s not just confined to lower, older leaves. We’re finding it active on the next layer of younger leaves. So there’s the potential for it to spread higher up the plant wherever there is rainfall, where it can start damaging yield.”

Mike Thornton, ProCam head of crop production, says he too is seeing high levels of Septoria tritici in the south – especially where a variety’s resistance rating is below six.

A lot of growers drilled wheat early last autumn because they had seed left over from the wet 2019 autumn, he says, so when September weather windows opened up, they were keen to get planted.

“With this heightened pressure, good Septoria tritici control from early-season fungicides is set to be particularly important to halt its spread onto higher yield-building leaves,” says Mr Thornton, “especially now we no longer have the stalwart fungicide, chlorothalonil, against the disease. 

“Although some new fungicide chemistry has curative ability, I don’t want to rely on this in case that increases the risk of resistance.

“There is an argument that says you don’t get a yield increase from controlling Septoria at the early T0 fungicide timing. That’s fine if you can guarantee you’ll be able to apply later sprays exactly on time. But very often you can’t.”

Mr Thornton says specific T0 fungicide options will vary depending on other diseases present, but he is generally looking to include a multi-site treatment against Septoria tritici of folpet, and potentially an azole if active yellow rust needs controlling, or a strobilurin for protection if yellow rust is a threat.

Nigel Scott says: “We are definitely seeing the effect of early drilling on Septoria levels clearly this season – both in trial plots and in the field. 

“At Cawood in Yorkshire, there is noticeably less Septoria in November-drilled wheat than in September-drilled,” Mr Scott adds.