Fungicide sprays at the T0 timing are a cost-effective tactic to control early disease, but the loss of epoxiconazole and flutriafol in the past five years has limited chemical options.

Of the options available, azoles remain a popular choice for early-season rust control.

But, with resistance fears on the rise, deploying a dual azole approach can help mitigate resistance taking hold.

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Mike Thornton, head of crop production at agronomy group ProCam UK, recommends the additional investment of a T0 spray to get on top of disease early on in the season.

With this, he also advises the use of different azole combinations to mitigate resistance risk.

Dual azole approach

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

“Combining two different azoles – for example, bromuconazole and 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.”

“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,” Mike adds.

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.

Later drilling windows seem to have exacerbated yellow rust disease pressure. If we are to see wet spring conditions, this could make it a struggle to apply fungicides.

Yellow rust has already been sighted in crops, continues Mike. Inoculum has been cycling in winter wheat crops, particularly Extase, Skyfall and Zyatt varieties.

“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.”

A combination of milder winters saw rusts cycle more quickly over winter, but brown rust pressure has dropped in the recent conditions that saw temperatures plunge below zero.

“Weather conditions over the past few weeks have certainly seen a shift in disease pressure, particularly brown rust.

“Conditions were initially looking like a repeat of last year, but with freezing temperatures at the start of March, this has now changed,” says Mike.

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 Simon.