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    Timings crucial as disease levels build in winter wheat crops
18/04/05

Clare Bend
Clare Bend
The timing of the first fungicide spray will be crucial this year to keep disease levels at bay in winter wheat crops, warns the Masstock group.

Poor weather has set back plans for many growers to get on early and apply a dose of fungicide to mop up the considerable levels of the main wheat disease Septoria tritici that have built up over the winter. Now that septoria is resistant to strobilurin fungicides, that have become the mainstay of many programmes, the timing of the T1 spray will be more important than ever, says Masstock technical manager Clare Bend.

“For those growers who haven't applied a T0, it will have to be spot-on,” she explains. “The T1 spray has to go on just as leaf three emerges. That means going out into the field and dissecting plants.”

Another approach is to feel the stem for the second node, which forms at growth stage 32. But this is a less reliable way of gauging the optimum timing than cutting the plant open to see if leaf three, an important yield-builder, has emerged, cautions Ms Bend.

“Ideally, you need to ensure maximum fungicide uptake occurs just as leaf three is emerging. Strobilurins once offered flexibility to the T1 timing, but Septoria resistance means that has now gone. We are already seeing quite a lot of infection in crops, which will have increased with the recent wet weather. So if you haven't applied a T0 spray, you will need a very robust T1.”

Growers should make good use of the welcome additions to the armoury to help in the battle against early season disease infections, she notes. Proline (prothioconazole) and Tracker (epoxiconazole + boscalid) offer good control of stem-based diseases, such as eyespot. “This is not everyone's number one priority, but the same package also delivers improved Septoria control. That means you can control the main early season diseases at a reasonable cost,” says Ms Bend.

Also new is Helix (prothioconazole + spiroxamine), which offers robust control of mildew, rusts and stem-based disease, plus exceptional Septoria tritici control.

“We have had reports of quite high mildew infections in wheat crops. Helix is particularly useful here and in high septoria risk situations.”

Rates of azole fungicides should be kept high, continues Ms Bend. This will help control of the likely high disease pressure. “Growers should also be aware of a drop in triazole activity on septoria. This means older products won't reach the same level of activity as some of the newer azoles, and there's less dose flexibility.”

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