Stubble management and weed control advice for North West and Midlands growers

Grace’s agronomy advice for October

1) Best practice for October Roundup^® applications to stubbles

Where Roundup^® applications to stubbles are still to be made in October, check target weed growth stages carefully and apply the appropriate dose. Italian rye-grass needs a minimum dose of 720g a.s./ha, for example, which should be increased if it has started to tiller.

Aim for a boom height of 50cm above the target and forward speeds of no more than 12km/h to get an even deposition on the leaf, while using a branded Roundup^® formulation helps ensure more reliable efficacy.

It’s important to give the chemical long enough to work before cultivating or drilling, and check for any survivors from a previous application. If there are any, don’t apply a second dose without using cultivations to destroy them first. It’s worth contacting your local agronomist to get survivors tested, especially of Italian rye-grass, where we know resistance issues are emerging.

2) Building robust pre-emergence and follow-up strategies for October drilling

Where wheat drilling has been delayed into October, which is most likely due to the presence of difficult grass weeds, a robust pre-em. herbicide application will be required. Soil temperatures in early October will still be warm, breaking down active substances faster. As the month progresses and temperatures reduce, products will last longer in the soil, but the chances of applying a top-up spray potentially diminish.

In both situations, that increases the importance of longer-lasting active substances, like aclonifen in Proclus® making it an ideal backbone of pre-em. weed control programmes for difficult grass weeds. Partner with a metribuzin co-form, such as Alternator® Met, Cadou® Met or Octavian® Met to bring in additional modes of action that will further boost grass weed control and apply within 48 hours of drilling.

The metribuzin brings an additional benefit in good activity on a range of broadleaf weeds, including some quite difficult-to-control weeds, such as cranesbill, groundsel and bur chervil, in trials.

Ideally, the initial pre-em. spray will be followed up around 10-20 days later with an early post-em. residual herbicide top up. In difficult grass weed situations, this is a good position for a cinmethylin product, while Liberator® is an alternative option, especially where grass weed pressure is lower.

Where wheat or winter barley were drilled into fields with grass weed concerns in September, a residual top up is an even higher priority than for October-drilled crops, as grass weed pressure will likely be higher.

Product choice will depend on what was applied at pre-em., so check labels carefully. Where the metribuzin co-forms weren’t applied at pre-em., for example, these would make a good choice for the follow up.

If grass weeds continue to emerge through the autumn, earlier applications of mesosulfuron-containing products, such as Atlantis® OD could also be considered, with results generally more reliable when applying to smaller weeds. That use does, however, limit options for any further grass weed control during the spring, so needs to be carefully weighed up.

3) How to manage strong autumn cover crops before spring drilling

I would expect cover crops growth to be strong this autumn, given a lot of growers were able to drill them in August following the early conclusion to harvest.

When and how to terminate is always a challenge, although the safest way usually is at least four weeks before you expect to drill your following cash crop, and using glyphosate at last as part of the method.

If there is a lot of biomass, then grazing depending on species within the cover crop mix or perhaps topping before glyphosate applications might be sensible. Remember to let the cover crop recover after to make sure the plant takes up the chemical.

Rates will be important – check our cover crop guide to species controllability for help in determining what rate to use – and tailor towards the most difficult species. If you haven’t grazed or topped, think especially carefully about water volumes and nozzle choice to maximise coverage and penetration to avoid the effects of shading.

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Alternator® Met, Cadou® Met and Octavian® Met contain diflufenican, flufenacet and metribuzin. Atlantis® OD contains iodosulfuron-methyl-sodium and mesosulfuron-methyl. Liberator® contains diflufenican and flufenacet. Proclus® contains aclonifen. Roundup® contains glyphosate. Alternator®, Atlantis®, Cadou®, Liberator®, Octavian®, Proclus® are registered Trademarks of Bayer. Roundup® is a registered Trademark of the Bayer Group. 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