Advice on T1 fungicides and other agronomy tips for April

Timing crucial for wheat T1 sprays

Go too early with T1 sprays and it won’t protect leaf three adequately, apply it too late and the risk is that disease is already established on the leaf.

Unfortunately, it’s also a tricky timing to correctly diagnose, requiring some good dissection skills to make sure it really is final leaf three that has emerged. But don’t just presume it is the right leaf.

There are two main choices from Bayer for the coming season, all covering the main disease threats of Septoria and yellow rust. How the crop looks will determine which is the best option for your situation.

For crops with excellent yield potential – perhaps early drilled – or high disease pressure, then our new fungicide this season could be worth considering. Plaxium® replaces the bixafen in Ascra® Xpro®with the new SDHI, isoflucypram,giving excellent control of the main winter wheat diseases.

Where crops are thinner, perhaps because of later drilling into poorer seedbeds, protecting yield is just as important. Thinner crops will still get disease, but growers understandably might be looking to spend a little less, but you still need to protect these crops otherwise you’re just knocking down yield potential even further. In this situation, Ascra® Xpro® is a great option.

Protect tiller to protect yields in winter barley

Retention of as many viable tillers as possible is critical for maximising yields in winter barley, and disease infections around GS30/31 are one cause of tiller abortion.

Fertiliser applications to the crop have caused some quick, lush growth which, together with weather, can be a recipe for disease infections. The main disease risks around T1 timing are Rhynchosporium, net blotch, brown rust and mildew, so it’s worth using a broad-spectrum fungicide, such as Ascra® Xpro®, that has multiple modes of action to protect crops.

Ascra® Xpro® can only be used once in winter barley crops[ND1] [MA2] , so I’d take advantage of that broad spectrum activity and use it at T1. If you’re thinking about using its Ramularia activity, it could be used at T2 with the possibility of using Siltra® Xpro® at T1, which is also a cost-effective at option at that timing.

More flexibility with Conviso® One sugar beet herbicides

If you’re using the Conviso® Smart herbicide tolerance system for sugar beet, there are some small tweaks to the Conviso® One label that will help make its use more flexible, although it must still be used as a single application.

Conviso® One can now be used from GS10 (expanded cotyledons) to GS18 (8 leaves unfolded), which is a slightly wider range of growth stage than previously, while it can also be tank mixed with an approved formulation of one of clopyralid, metamitron or ethofumesate.

However, we would still recommend that Conviso® One is used in sequence rather than tank mix, although mixing is potentially helpful [ND3] with workloads. Using alternative modes of action will also help protect against resistance development – poppies, chickweed and mayweeds are weeds to be especially aware of when using the Conviso® system.

For conventional varieties of sugar beet, Betanal® Tandem® remains an effective mostly contact-acting herbicide that can be used from expanded cotyledon stage of the beet. First applications at that stage should be used at 1.0 L/ha in tank mix with a residual like metamitron, while for subsequent sprays the dose can be increased to 1.5 L/ha. If you’re adding oil, remember the guidelines for dose will depend on the expected high temperature on that day.

Potato weed control most effective at pre-emergence

It’s helpful to know likely weed species and burdens from previous field history, if available. Around the Nottinghamshire / South Yorkshire area there are sometimes some very localised weed populations, which ideally will have been reduced or controlled before planting.

Residual herbicides applied pre-emergence tend to give the most effective control of weeds in-crop, with Emerger® proving to be a useful tank mix partner at the timing. Partner[ND4] s to consider with it include Artist®, which will broaden out both grassweed and broadleaf weed control, or Sencorex®, provided your potato variety is tolerant to metribuzin.

Remember Emerger® is pre-emergence only and needs to be applied at least seven days before crop emergence. Optimise application for best results – apply to uniform ridges and avoid cloddy seedbeds as these will shelter the weed seeds within the clod from the herbicide to emerge at later date.

Protecting remaining oilseed rape potential

Oilseed rape crops have been hammered by pigeons after escaping the worst of the flea beetle damage this season, so many are looking a bit worse for wear currently.

Where crops are being taken through to harvest, protecting remaining yield should still be justifiable. Aviator® Xpro® will help protect against Sclerotinia and top up light leaf spot control. It can be applied either as a single application or split into two treatments, with the first as first petals fall from flowers at a rate of 0.75 L/ha. This can then be followed up if flowering extends past the three weeks protection with a further dose of 0.5 L/ha.

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Artist® contains flufenacet and metribuzin. Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Aviator® Xpro® contains bixafen and prothioconazole. Betanal® Tandem® contains ethofumesate and phenmedipham. Conviso® One contains foramsulfuron and thiencarbazone-methyl. Emerger® contains aclonifen. Plaxium® contains isoflucypram, fluopyram and prothioconazole. Sencorex® contains metribuzin. Siltra® Xpro® contains bixafen and prothioconazole. Vimoy® contains isoflucypram.

Artist®, Ascra®, Aviator®, Betanal®, Conviso®, Emerger®, Plaxium®, Sencorex®, Siltra®, Tandem®, Vimoy® and Xpro® are registered Trademarks of Bayer. All other brand names used are Trademarks of other manufacturers in which proprietary rights may exist. Use plant protection products safely. Always read the label and product information before use. Pay attention to the risk indications and follow the safety precautions on the label. For further information, including contact details, visit www.cropscience.bayer.co.uk or call 0808 1969522. © Bayer CropScience Limited 2025