A lot of effort has gone into managing wheat crops during this difficult spring. However, getting the T3 spray wrong could undo much of this good work and put income at risk.
Ear blight-causing species Fusarium culmorum and F graminearum produce the mycotoxins deoxynivalenol (Don) and zearalenone (Zon), and there are legal limits for both.
High levels can lead to the loss of milling premiums, or even crops being rejected altogether.
While other species such as Microdochium nivale do not produce mycotoxins, they can have a severe impact on grain yield and specific weight, as seen in the harvest of 2012.
Therefore, it’s important for farmers to manage the risk at the T3 fungicide timing.
Prevention – trials with angled nozzles
Phil Jennings, plant pathologist at Fera, says he is already seeing microdochium at the stem base and Fusarium culmorum on lower leaves.
“You would not normally see F graminearum yet, but current dry conditions have been favourable for it,” he adds.
Dr Jennings highlights that it is all about prevention – and this relies on getting good coverage of the ear with a fungicide.
“Ideally you need to fully coat the ear. Then you have a better chance of stopping infection,” he says.
He recalls a trial where they coated one side of the ear and still saw disease development on the other side.
The need for good coverage led Dr Jennings to carry out trials with angled nozzles.
“Our work has shown that that angled nozzles improve control,” he says.
He tested angled nozzles versus vertical flat fans and saw a consistent response from Proline (prothioconazole), Folicur (tebuconazole) and Prosaro (prothioconazole + tebuconazole).
For example, with tebuconazole fusarium severity fell from 24% to 15% just by the switch to an angled nozzle.
Sprayer operator Matt Redman has gone a step further by fitting angled nozzles (Defy 3D), alternating forwards and backwards facing.
“This is so we can coat both sides of the ear as the sprayer travels through the crop,” he explains.
Mr Redman has about 600ha of winter wheat in Bedfordshire and Cambridgeshire that he will be applying a T3 to this season.
Matt Redman’s approach to T3 spraying
Nozzle: Defy 3D, alternating forwards and backwards
Volume: 100 litres/ha
Speed: Forward speed of 12-14kph.
Boom height: 50cm above the crop
Ideal timing – tight window
The other key part of a successful T3 spray is timing, as the window can be just a matter of a few days. Sam Harvey, Bayer’s commercial technical manager, says the ideal timing is early to mid-flower at growth stage 63.
“Work with Fera identified this as the ideal timing. Plants start to flower at the centre of the ear and this is the time to go in for maximum protection. You are applying before disease starts to penetrate via the anthers.”
He warns that if farmers leave it to growth stage 65, the fungus may already be in the ear.
“Conversely if you go too soon, you will not coat the anthers and this route of entry is exposed.”
This season, the high variability of crops in fields will make timing more difficult, as you are not going to hit the optimum time for all plants.
Mr Redman says he goes by the majority of the field, as “this is where most of the yield potential is”.
Finally, on fungicide choice, Dr Jennings says azoles like metconazole and tebuconazole offer good control of Fusarium culmorum and F graminearum.
However, prothiconazole is the only azole that is effective for both fusariums and microdochium.
Know your enemy
Knowing which species are present in your crop allows you to take the right action, thereby minimising the number of rejections. Read our guide to the different species for an in-depth look