Responding to fertiliser costs with T1 fungicides

Product Update
Young winter wheat

Have higher fertiliser costs increased the importance of an effective T1 fungicide strategy?

So, you have bought this season’s fertiliser, or are planning to. And the bill appears substantially higher than a few years ago. How do you get the best return on this investment?

According to Syngenta UK head of technical, David King, the combination of healthier grain prices but increased fertiliser costs over recent years has raised the financial stakes of growing crops – so any ‘mistakes’ that allow yield-robbing diseases to gain a foothold can pose a bigger crop margin threat.

Benefit from fertiliser

“Grain prices have declined slightly recently, but they still remain strong,” says Mr King, “and clearly appropriate nitrogen (N) use is essential for crops to reach their full yield potential. However, to get maximum benefit from that fertiliser expenditure, it’s essential to minimise the amount of yield that’s lost to disease.

“The flag leaf in winter wheat contributes the most to yield, at about 43%, so keeping this clean of disease is paramount, but waiting until T2 to do this is missing the boat. Disease prevention starts earlier – potentially at the T0 timing, but certainly at T1.”

Although leaf three, which is the spray target for the T1 fungicide, contributes less than 10% to winter wheat yield, Mr King says it plays a far more strategically important role than its yield contribution suggests.

Yield and T1

“Leaf three is effectively a bridge between any disease lurking in the base of the crop over winter and the upper yield-building leaves – making T1 a pivotal timing. Combined together, the top three leaves contribute about three quarters of final winter wheat yield.

“Think of a T1 fungicide as a firebreak to restrain the upward spread of infection to leaf two and the flag leaf. By using an effective T1 fungicide to achieve this, you stand to get better results from your T2 fungicide because it will be used more preventatively,” he adds.

Mr King says although recent years have seen a greater appreciation of the importance of T1 – partly driven by increased awareness of difficulties ‘controlling’ Septoria tritici later, and bitter experiences of managing yellow rust – the need to get the best return from fertiliser brings its importance into even sharper focus. “It’s vital to protect that fertiliser investment,” he stresses.

Yellow rust

“Yellow rust has become more unpredictable. It can flare up rapidly and we’ve seen how suddenly variety resistance ratings can tumble. Yellow rust also isn’t just an Eastern counties disease.”

Yellow rust on flag leaves

Where yellow rust poses any kind of threat around T1, Mr King suggests that the SDHI-based fungicide Elatus Era is a ‘no-brainer’. AHDB dose response curves demonstrate its outstanding activity against yellow rust, he says, although to pigeon-hole it as a rust-only treatment is to miss out on its other benefits.

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Chief among these, he says, include the way its active ingredient (benzovindiflupyr also known as Solatenol) has been shown to interact with the leaf – which is important when it comes to managing Septoria tritici and for providing persistence.

Mr King explains: “While certain fungicides move up the leaf gradually after application, others move rapidly and can accumulate in the leaf tip. The concern with this accumulation is that it leaves areas towards the leaf base less well protected. This is important because Septoria infection often begins around the leaf base where moisture collects.

SDHI fungicides

“In research, we’ve seen clear differences between SDHI fungicides and their leaf behaviour. Usefully, Solatenol is relatively slow-moving and has been shown to produce an even distribution of fungicide along the leaf length. As well as complete leaf protection, this contributes to long-lasting results, which is important for a T1 fungicide in case adverse weather means the T2 fungicide is delayed.”

As well as using an effective SDHI at T1, Mr King says adding the multi-site fungicide folpet is also an important consideration for managing Septoria tritici resistance.

David King, Syngenta UK head of technical

“We’ve had a wet winter this season, which will favour Septoria tritici pressure. Also, a proportion of winter wheat crops were drilled late last autumn after the drought, and we know that smaller wheat plants can be harder hit by yellow rust.

Brown rust

“Although it doesn’t normally manifest until later, the other disease to be aware of is brown rust. Elatus Era is also effective against brown rust,” he adds.

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In field situations where disease pressure appears low at the T1 timing, Mr King admits it can be tempting to ease back on T1 fungicides. However, a key aim of T1 is to protect the crop forward, he stresses, and recent seasons where weather conditions have turned favourable for disease after T1 have repeatedly underlined how skimping on T1 can catch people out.

“Nitrogen gives one of the best returns among inputs, but it’s important to protect this investment by minimising disease. An effective T1 fungicide becomes even more important if you’ve not controlled disease at T0,” he adds.

Example T1 winter wheat fungicide strategy

Timing: Leaf three 80% or more emerged

Core treatment: Elatus Era + folpet

Possible partner: Add Amistar to above if additional rust protection and take-all activity needed

Source: Syngenta