‘Don’t undervalue T0 spray in winter wheat’

• Early action can pay dividends

• Disease control is key challenge

• Choice and timings important

Growers are being advised to tackle rust problems early in winter wheat crops – or risk paying the penalty later.

Mike Thornton, head of crop production at ProCam UK, says recent mild winters followed by cool, wet springs mean both brown and yellow rust are cycling more quickly – leading to higher levels of inoculum in crops at the T1 spray timing.

Later drilling windows embraced by many growers to ease grassweed pressures have also exacerbated yellow rust issues – making early season cereal disease control a much greater challenge.

Better prospects

“It’s a difficult conundrum for growers,” says Mr Thornton.

“Later drilling offers them better prospects for septoria control but, conversely creates a greater risk of yellow rust because crops are usually under more stress at that point given their root systems are not as fully developed.”

Wet spring weather and sodden fields can make it a struggle to get a T0 fungicide spray on to crops in March.

But Mr Thornton says the additional investment and security of a T0 spray is worthwhile to get on top of rust and other key diseases earlier – helping to reduce resistance risk and protect yields later.

The loss of epoxiconazole and flutriafol means T0 options for growers are more limited than they’ve been in the past. But there are still a number of good actives out there 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, making disease control potentially more difficult.

Disease scenarios

“Combining two different triazoles, such as bromuconazole + tebuconazole, in azole-based products such as Soleil is a solid option for combating rust at T0. It also means not selecting as vigorously for the same septoria strains.

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

“Different rust populations come with different sensitivities, so 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, says Mr Thornton.

Simon Leak, crop solutions manager for Sumitomo Chemical, supports Mr Thornton’s call for growers to reconsider the use of a T0 spray to reduce rust development until the T1 timing.

“T0 is generally a cost-effective holding spray to control early rust and hold back septoria before the first main spray timing at T1. Of all the options, triazoles are still the most popular. They also offer some activity on septoria and eyespot.”

‘Solid option’

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 fusarium control at T3, says Mr Leak.

“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.”

Changing the triazole mix to improve resistance management is sensible given that different azoles are active on different septoria strains. It’s also better than the same azole throughout a fungicide programme – albeit in mixes with other chemistry.

Disease scenarios

“Controlling both brown and yellow rust effectively is a significant challenge,” says Mr Leak – especially given the possibility that tebuconazole may disappear from the armoury in the future.

The answer may come from a new active ingredient from Sumitomo known as Indiflin (inpyrfluxam), currently in the regulatory system. An SDHI, it is already on the market globally, targeting diseases such as soybean rust.

“Indiflin will, in general, be used at T1 or T2 for the control of yellow and brown rust. It has excelled in UK trials – even when up against the severe brown rust infections that many growers experienced during the 2024 harvest season.”