Wheat disease control needs to be spot-on in late spring

Winter wheat growers need to be ready with key fungicide sprays later this month as warmer weather follows a slow start to spring.

Cooler weather delayed the timing of early season T0 fungicides by about a week, but crops are catching up and could be ready for T1s by late April.

The gap between these first two sprays may be as short as two weeks this season, so growers need to be ready with T1s especially on early-drilled crops.

See also: Septoria is the big disease threat to wheat this spring

The T1 timing is when wheat stems have two nodes more than 2cm apart (GS32), but more accurately it is when leaf 3 is almost fully emerged.

Jonathan Blake, fungicide expert at crop scientist group Adas, says some early drilled crops may only be a week away from T1 with the current warm weather.

“This T1 spray is important to create a firewall and stop any disease epidemic reaching the leaves above leaf 3,” he tells Farmers Weekly.

Tim Nicholson, commercial technical manager at Bayer CropScience, says the gap between TOs at the end of tillering (GS30) and GS32 this season could be as short as two weeks.

“We would advise growers to get out into the field and look for the emergence of leaf three and not leave the T1 spray too late,” he says.

Mr Nicholson adds although the lack of rain has held back the development of wheat’s most destructive disease septoria, strong overnight dews can help spread the disease.

With a shorten gap between T0 and T1, he suggests growers could save £6-£12/ha on fungicide bills when in a protective mode rather than a curative one.

Some growers used just the protectant fungicide chlorothalonil at T0 as they didn’t need a rust-active azole, saving them about £6/ha, Mr Nicholson adds.

A further saving of £6/ha could be made by chosing a straight azole such as prothioconazole plus chlorothalonil rather than a SDHI/azole product.

He cautioned that a SDHI/azole approach would be needed if the T0 was missed or if the T1 spray is delayed.

Christine Lilly, technical support manager at distributor Frontier, says septoria is being seen in early-drilled crops in her area of Lincolnshire and yellow rust in untreated trial plots.

After the high disease risk year in 2014, she suggests many growers will go for a SDHI/azole spray at T1, apart from later-drilled crops of more resistant varieties.

“Crops are around 10 days behind last year, but some early-drilled early-maturing varieties like Skyfall and Gallant are close to seeing leaf 3,” she says.

Ms Lilly estimates the gap between T0 and T1 could be about three weeks which will be more manageable than last year when very early T0 sprays meant the gap was often four to five weeks.