Disease risks, particularly from yellow rust, and physiological responses in dry conditions are prompting some agronomists in the East to consider recommending treating wheat with a newer SDHI fungicide at T1 this spring.

Their use can help with rooting, giving better access to water, suggests research, although the lack of moisture at depth means that not all crops will respond.

“The question that keeps cropping up this spring, due to the dry conditions, is whether we should consider the use of an SDHI early in the programme at T1,” says Bill Clark, commercial technical manager at NIAB TAG.

“And the answer is probably.”

While the older SDHI containing boscalid products at T1 will give the desired greening and rooting effects alongside disease control, the results from newer SDHIs at that timing will be even better, he notes.

“These products help plants cope with moisture stress. In a normal UK drought situation, which tends to be transient, they will be useful. But if we have another year as dry as 2011, it’s more difficult to predict whether they’ll make any difference.”

Also relevant is the fact that crops infected with yellow rust drought off quicker, points out Mr Clark. “That’s because yellow rust disrupts the leaf cuticle, meaning that the crop loses lots of water. So on lighter soils particularly, it’s important to keep the disease out.”

Yellow rust infection is the reason that Bedfordshire-based ProCam agronomist Steve Wolff is considering the use of Syngenta’s Seguris (isopyroxam + epoxiconazole) at T1, predominantly on Oakley.

“Yellow rust was showing very early on around here,” he says. “And the yellow rust activity of Seguris is interesting. It’s possible to get good results at relatively low rates.”

He will be trying 0.5-0.6 litres/ha of Seguris with some additional epoxiconazole and chlorothalonil at T1 to see how it performs.

At this stage, any reduction in moisture stress is of less importance. “But we’ve seen the effect of the active ingredient, isopyrazam, on barley at T1, which was much greener. So we know it helps, but we’re not certain if there’s a yield benefit.”

His alternative is to use boscalid tank-mixed with a strobilurin at T1, as products such as pyraclostrobin have good rust activity and also bring greening benefits.

“That means that we will be using two SDHIs in a number of situations, as we’ll follow up with one of the three newer SDHIs at T2.”

Whichever option he decides on, efforts will be focused on keeping four-week intervals between sprays. “The T0s have gone on in good time and we may well start our T1s a bit earlier, especially where Oakley is being grown.”

Independent agronomist Richard Palmer of Farm Vision believes that early use of strobilurins will give the required rust activity.

“The main slot for a strobilurin is at T1 this year,” he says. “Then an SDHI will be considered at T2, but not before.”