A number of wheat varieties have seen their septoria ratings fall, which will require a more robust approach to disease control to avoid yield losses – which can be as high as 50% if left unchecked.

The Septoria tritici epidemic last year saw many varieties’ one-year ratings fall from their three-year ratings on the 2021-22 Recommended List.

About one-sixth of varieties have fallen by more than one point, on the 1-9 scale.

See also: Two new fungicides to fight septoria in wheat grower’s plans

For example, Firefly had a three-year figure of 6.8 on the 2021-22 list and the single-year figure on the current list is 4.9.

However, as varietal resistance is the first line of defence against the disease, growers face having crops that are at greater risk and will need a proactive management plan in place.

Syngenta crop disease specialist David Ranner outlines his five-point checklist for growers with higher- risk crops.

1. Factor in drilling date and location

As well as checking a variety’s latest Septoria tritici resistance rating, consider its drilling date when assessing risk, says Mr Ranner.

Septoria levels can be much higher in September-drilled wheat than those drilled in October, he notes.

Some crops were drilled early last autumn as growers took advantage of the dry September.

“Clearly, the weather also plays a huge role in how septoria develops, so later drilling won’t eliminate risk, but earlier drilling allows it longer to build up over winter.

Thicker crops from earlier drilling also encourage its spread between leaves via rain splash.”

In wetter areas in the West or North, growers need to be particularly careful with less resistant varieties, he adds.

2. Prevent rather than cure

It is difficult to cure septoria once established, says Mr Ranner, so it is particularly important to adopt a “keep it out” approach to control.

Fungicides generally work better as a preventative measure.

He says: “Historic glasshouse research by Adas for Syngenta, comparing SDHI + azole fungicides, showed much better septoria control with treatments applied preventatively, seven days before leaves were infected, than curatively, seven days after.”

This was still evident seven weeks after application, he adds.

“With good grain prices and the top three leaves in winter wheat contributing three-quarters of the final yield, there’s a strong case for a long-lasting fungicide at the important T1 timing to start protecting these leaves.”

3. Recognise the value of a T0

Do not overlook the benefit of using a T0 fungicide, typically applied in March, to suppress infection that has come through the winter, says Mr Ranner.

“Reducing early disease pressure with a T0 also increases the likelihood that the T1 fungicide will be applied preventatively for better results.”

4. Maintain correct fungicide timings and doses

A variety that is less able to resist infection requires well-timed fungicides to stay on top of disease and potentially higher fungicide doses.

“Monitor crop growth stages carefully,” says Mr Ranner.

“This isn’t only to guard against fungicides being applied too late after infection has built up, it’s also to ensure the correct leaf is being targeted.”

At T1, there’s no substitute for dissecting the plant and counting the number of leaves yet to emerge to check you are actually treating leaf three.

5. Build in multisite protection

With heightened disease risks, it is beneficial to include a proven multisite fungicide in the programme, targeting septoria at multiple points in its metabolism, says Mr Ranner.

“As well as providing a different mode of action to protect single-site fungicides against resistance, adding the multisite folpet to a range of other fungicides in trial plots in 2021 was shown to both improve septoria control and increase yield.”