Filling the gap in T0 spray programmes

Early-season wheat disease management and traditional T0 programmes are not what they used to be. With the loss of key fungicides like chlorothalonil, growers have faced a gap in their disease control plans and a lack of will to invest in other T0 options. But that is changing. With the emergence of plant health elicitors - like those discussed in our recent webinar on wheat disease control - experts, agronomists and growers are exploring the potential possibilities and benefits of T0 fungicides. Why is T0 important? T0 is typically applied at growth stage 30 onto a fully emerged leaf four. Although this leaf doesn’t contribute much to the final yield, a heavily infected leaf four does have ramifications throughout the rest of the crop’s growth. It helps septoria and yellow rust spread up through the canopy, and leaves agronomists and farmers chasing disease for the rest of the season. Previously, chlorothalonil (CTL) was a perfect fit for T0. Cheap to apply, low resistance risk and highly active against septoria, it protected the leaf and suited fungicide use throughout the rest of the programme. The new and improved options for T0 With the revocation of chlorothalonil (CTL), plant health elicitors like IODUS (laminarin) are filling the gap. IODUS works by mimicking degraded cellular material released from a fungal attack, stimulating a plant’s own defence mechanisms to protect it from future infection. Better still, it moves throughout the whole plant, so you don’t need to reapply it onto newly emerged leaves. Applying IODUS before a fungal pathogen attack prepares the plant for when an actual infection occurs. And it extends its protection past T0, potentially offering even more benefits than CTL. Stuart Jackson, UPL’s head of technical services, explains: “A litre of CTL at T0 gave farmers three to four weeks protection of leaf four and dampened down any existing infections in the crop, giving flexibility for the T1 application. However, when leaf three emerged, it was completely unprotected until the T1 was applied because the CTL wouldn’t transfer onto it.” “The key difference with laminarin (the active in IODUS) at T0 is that you already have the protection on the newly emerged leaf. Once you apply it at T0, the active moves through the whole plant and tells leaves three, two and the flag leaf, hidden in the sheath, to prepare for an infection.” The benefits of IODUS at T0 Applying IODUS at T0 has a beneficial impact on disease control throughout your entire programme. It gives you more flexibility with fungicide timings, because you’ve already primed the defences of those newly emerged leaves. You get more leeway, which is going to be a huge asset with the variable crops this year. IODUS also has good tank mix compatibility, which is important as T0 comes at a time when farmers might be looking to apply herbicides, trace elements and plant growth regulators. “If you need to do spring grass weed control, and there will be lots of these situations this year because of the autumn weather, it is one of the products that you can include with mesosulfuron herbicides like Horus (mesosulfuron + iodosulfuron). It is a relatively benign product, so I wouldn’t expect it to cause an issue, which is another benefit of it in the T0 slot,” says Antony West Wade, Agrovista technical manager for the West. With an early T0 application of IODUS, you might also be able to reduce doses of your T1 fungicide, potentially cutting costs and improving margins. That’s what the results of ADAS trials in Herefordshire found. IODUS in the field with ADAS IODUS was trialled in two crop varieties - Elation and Graham. Elation is highly susceptible to septoria, and was sown 28th of September to increase the exposure to disease. Graham was lower pressure, a typical commercial crop, sown on 13th October. In Elation:

Average of 56% disease control across leaves 1, 2 and 3 in the the untreated crop
Good dose response rate to the different Ascra Xpro (bixafen + fluopyram + prothioconazole) rates used at T1
Adding IODUS at T0 improved disease control
Especially beneficial at the lower doses of Ascra Xpro

“The curves on our yield graph showed that adding IODUS and THIOPRON had a benefit of about 0.2 to 0.3 T/Ha. We calculated the margin using wheat at £200 /T and the approximate costs of the products used, and this pulled the results out even further,” says Ella Bradfield, crop pathology consultant for ADAS. In Graham:

Average of 34% disease across leaves one, two and three on the 20th of June
Clear difference in the disease control improvement by adding Iodus at T0 and Thiopron at T1

This season, ADAS will be trialled IODUS at T0 across even more varieties, to compare the benefits depending on the disease resistance of the variety. You can find out more about IODUS here.