Higher levels of brown and yellow rust inoculum are cycling in winter wheat crops, which may prompt wider-scale use of a T0 spray to hold off disease pressure.

Following a combination of milder winters and wet spring conditions, rusts are cycling more quickly over winter.

This is leading to higher levels of rust inoculum in crops at T1 says Mike Thornton, head of crop production, at agronomy group ProCam UK.

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Mr Thornton recommends the additional investment of a T0 spray to get on top of disease early, reduce resistance risk and protect yields.

To mitigate resistance risk in early fungicide sprays, he advises growers to use different triazoles.

Dual triazole approach

Later drilling windows seem to have exacerbated the disease pressure issue and made early season control more challenging. What’s more, wetter springs makes it a struggle to apply fungicide sprays.

“It’s a difficult conundrum. Later drilling offers better prospects for septoria control, but creates greater risk of yellow rust because crops are under more stress at that point, given that root systems are not fully developed.”

With the loss of both epoxiconazole and flutriafol in the past five years, chemical options for growers at T0 are limited. However, there are still a number of actives for early season rust control.

“A dual triazole approach is preferable to a single triazole to avoid situations when use of a single triazole can inadvertently select for certain populations of septoria,” says Mr Thornton.

“Combining two different triazoles, for example bromuconazole + tebuconazole in an azole-based products such as Soleil, offers a solid option at T0 for combating rust but also means you don’t select as vigorously for the same septoria strains.”

This helps to avoid serious disease scenarios later in the spring – particularly when dealing with a forward crop with septoria present, a variety with low resistance to septoria, or if the grower is in a higher risk septoria area.

“Different rust populations come with different sensitivities, so developing good resistance management strategies within any fungicide programme comes down to mixing different actives to gain the broadest spectrum of control and reduce risk.

“Using different azoles at T0, such as bromuconazole and tebuconazole, also takes the pressure off more popular azoles such as prothioconazole that are often being used as either a straight or within mixes at both T1 and T2” Mr Thornton adds.

Cost-effective holding spray

Simon Leak, business manager crop solutions for Sumitomo Chemical (UK), advises growers to reconsider the use of a T0 spray to hold off rust until the T1 timing.

T0 is generally a cost-effective holding spray to control early developing rust and hold back septoria before the first main spray timing at T1.

Of the options out there, triazoles are still the most popular.

They are cost-effective and offer some activity on septoria and eyespot.

Soleil (bromuconazole + tebuconazole) is a solid option at T0 for its control of rust and eyespot but can also be applied up to growth stage 65 as it delivers very good Fusarium control at T3.

“It’s a flexible tank mix option, can be applied in all soil conditions and performs equally well on both winter and spring wheat, rye and triticale,” says Mr Leak.