Helpful weed and disease control advice for northern growers

1) How to follow up autumn residuals in wheat

Unlike last year, most growers were able to apply autumn residual herbicide sprays and for the most part they seem to have worked very effectively. That’s good news as it means we won’t be firefighting with mesosulfuron as much.

But it will still be important to walk fields on an individual basis to monitor for further weed emergence. If you’re expecting further grassweeds to emerge there’s the option to lay down additional residual, for example, with one of the metribuzin-containing products where the metribuzin also gives some contact activity. These products can be applied up to GS25.

They can also be tank mixed with a contact herbicide containing 12g/ha of mesosulfuron, such as Atlantis® OD, or if the grassweeds are past one-leaf stage a mesosulfuron-containing product can be used alone in mix with the adjuvant Biopower®.

In March you can apply the full 15g/ha mesosulfuron dose in both Pacifica® Plus and Atlantis® Star, which will cover black-grass, Italian ryegrass and brome.

2) Check wheat variety rust ratings

Wheat crops drilled in the early September window may need some help with Septoria control at T0 (GS30), unless they have a very good resistance rating. There are fewer good options for Septoria control at this timing without chlorothalonil, with choices limited to folpet or an elicitor.

Later drilled crops will be more at risk from yellow rust – I’ve heard some reports of yellow rust in Dawsum in the Durham area already. Check variety resistance ratings – although be aware juvenile susceptibility can be different and that adult plant resistance doesn’t always kick in as early as you’d hope. Prevention is definitely better than cure with yellow rust – the best option for control at T0 is probably tebuconazole at 0.5 L/ha. If brown rust is present, increase the rate to 0.75 L/ha and add in a three-quarter dose of a strobilurin, such as azoxystrobin.

3) Protect tillers in winter barley

Winter barley yield is set through maximising grains per square metre through keeping as many viable tillers as possible. Disease infections around GS30/31 are one of the reasons why barley crops will abort tillers, making T1 timing the most important in the crop. The loss of a barley tiller cannot be compensated by remaining ears setting more grain the way it can be in wheat.

That makes the return on investment greater typically from T1 in winter barley. Key diseases to watch out for include net blotch, Rhynchosporium, brown rust and mildew. Both Ascra® Xpro® and Siltra® Xpro® are good allrounders that fit nicely as T1 sprays, providing cost-effective control.

4) React to glyphosate resistance finding

The finding of three Italian ryegrass populations with resistance to glyphosate is a worry, and a wake-up call, if we needed it, about the risks of resistance developing.

Not all poor control with glyphosate will be the result of resistance though. Last year, some issues were caused by delayed sprays where rates were not adjusted to take into account larger weed sizes, and poor conditions impacting weed growth and affecting take up of the product.

Care with applications is needed too – it’s not a job to be rushed, even if it sometimes feels like glyphosate is so effective that application technique doesn’t matter as much.

Key factors to consider:

• Match rate to weed size and species difficulty to control

• Concentrate on good application practice – don’t be tempted to go too fast, use the correct nozzles, water volumes and boom height

• Monitor for survivors and prevent seed return

• Don’t spray any survivors with a second glyphosate dose – control using cultivation or another alternative method

5) Test for light leaf spot

With some decent potential in oilseed rape crops this season, getting on top of damaging diseases such as light leaf spot as soon as possible makes sense. It’s another disease that is particularly difficult and more expensive to control once it is established in the crop.

It’s also not that easy to spot in crops at early stages – the best method remains putting leaf samples in a plastic bag in a warm place for a few days to encourage any symptom development.

If you find any infection then treating with Aviator®, Proline® or tebuconazole, if you need growth regulation, before flowering should be considered.

6) Organisation will help if growing Conviso® sugar beet

Sugar beet drilling will likely be earlier this season, assuming weather is favourable, without the delay for treating seed with neonicotinoids.

If you’ve chosen a Conviso® Smart herbicide tolerant variety for the coming season, responsible use is fundamental to the longevity of its benefits. Do not mix Conviso® Smart and conventional varieties in the drill – only sow whole fields with Conviso® Smart seeds. You can tell a Conviso® Smart variety by its purple inner seed colour.

Other pointers include not drilling areas of fields that cannot be lifted by a harvester as this creates a risk of groundkeepers in following crops, while communication with the on-farm team is crucial. Mark fields either physically or on mapping software operators use to avoid killing conventional varieties with the Conviso® One herbicide.

7) Option to use Emerger® on beans and combining peas

If you’re planning to grow field beans or combining pea crops this season, weed control can be challenging given the uncompetitive crop canopy during early establishment and limited number of herbicides authorised in these crops.

To improve weed control, Emerger® can be applied pre-emergence in field beans and combining peas at 1.4 L/Ha with a herbicide tank mix partner.

Emerger® contains the active substance, aclonifen, which is taken up by the shoot of emerging weeds and translocated to the meristems, aiding weed control in dry conditions and improving consistency. It has good activity on fat hen, red shank, black bindweed, mayweeds, charlock, chickweed and poppy, while improving control of annual meadow-grass and black-grass.

For optimal uptake, Emerger® should be applied uniformly to the ground to form a homogenous film, meaning friable and level seedbeds aid efficacy.

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Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Atlantis® OD contains iodosulfuron-methyl-sodium and mesosulfuron-methyl. Atlantis® Star contains iodosulfuron-methyl-sodium, mesosulfuron-methyl and thiencarbazone-methyl. Aviator® Xpro® contains bixafen and prothioconazole. Biopower® contains genapol. Conviso® One contains foramsulfuron and thiencarbazone-methly. Emerger® contains aclonifen. Firefly® contains fluoxastrobin and prothioconazole. Pacifica® Plus contains amidosulfuron, iodosulfuron-methyl-sodium and mesosulfuron-methyl. Proline® contains prothioconazole. Siltra® Xpro® contains bixafen and prothioconazole.

Ascra®, Atlantis®, Aviator, Biopower®, Conviso®, Emerger®, Firefly®, Pacifica®, Proline®, Siltra®, 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