October agronomy tips for weed control, weed beet management and cover crop destruction for Northern growers

Tom’s agronomy tips for October

1) How to manage grass weeds with Roundup® before October drilling

After the last couple of difficult autumns for drilling, I imagine most growers will be trying to get drilled up as quickly as possible, so unless weather intervenes in the latter half of September, October drilled wheats will be in the minority.

Where drilling has been delayed into this month, take advantage of what should be continued good emergence of grass weeds, given the low dormancy and moisture in seedbeds. Ideally spray off with Roundup® either at least 10 days before drilling to break the green bridge for barley yellow dwarf virus infections, or if you’ve already applied the first spray, around drilling. Remember to use cultivations to destroy any survivors from first sprays, this is particularly important if you have Italian rye-grass where resistance to glyphosate has been confirmed, but also with other weeds.

Where you use glyphosate close to drilling, check labels for rates, as there are restrictions to a maximum dose of 540g a.s./ha for products used within 48 hours of drilling or mixed in with a pre-emergence after drilling.

2) Choosing the right pre-em. and follow-up sprays in early drilled wheat

Sticking with October drilled wheat crops, herbicide programmes will depend on the weeds present. Where difficult grass weeds: Italian rye-grass, black grass and bromes are not present, then a half rate Liberator® plus partner to widen out broadleaf weed spectrum at pre-em. should be a good start.

If you have slightly more difficult broadleaf weeds, like bur chervil and groundsel, it’s worth considering the metribuzin co-forms, Alternator® Met, Cadou® Met and Octavian® Met, as trials have shown these products have good activity.

Both Liberator® and metribuzin co-forms provide flexibility in that they can be used early post-emergence if you miss the pre-em. window.

If you have any of the difficult grass weeds, then the pre-em. becomes vital. The addition of Proclus® to either the metribuzin co-form or Liberator® provides a solid first spray option, ideally applied within 48 hours of drilling. Proclus® will provide extra longevity of activity, plus another mode of action.

For September drilled wheat crops, hopefully the pre-em. will have already been applied, but where you have difficult grass weeds, it’s almost certain that you will need to top up control this autumn. Earlier drilling means warmed soil temperatures and quicker breakdown of active substances.

What to follow up with depends on what the pre-em. was, as there are restrictions on the number of applications for some products. If the metribuzin co-forms weren’t applied at pre-em., these could be a good option to consider, the metribuzin gives a little bit of contact activity against both grass and broadleaf weeds.

3) Managing high-biomass cover crops for effective termination

It’s been a good year for overwinter cover crops. The early harvest allowed them to be drilled in good time in August, with support payments from SFI and Countryside Stewardship schemes offsetting costs, if you were lucky enough to be in such a scheme.

August drilling should create higher biomass crops through the autumn, helping improve soil health and mopping up excess nutrients. But it also does create potential challenges with termination after Christmas. Some growers will look to graze, which will help remove biomass. Topping, mowing or rolling on a frost can also help reduce top growth before spraying off with Roundup®.

With glyphosate sprays, whether as a standalone or following grazing, mowing or rolling, always check for what will be the most difficult species to kill off and tailor rates to those plants. Our Cover Crop Guide from a few years ago will help provide suggested rates for most common cover crop species.

Ideally, look to terminate cover crops 4-6 weeks ahead of drilling a spring crop.

4) Protecting Conviso® Smart sugar beet: Stop weed beet before it starts

There’s more Conviso® Smart sugar beet in Yorkshire this season, with some new growers.

To maintain its effectiveness for the future, it’s important to manage the system, including groundkeepers and bolters effectively – otherwise you risk having weed beet challenges all over again.

Ideally plough after beet crops to make sure beet tops don’t regrow, monitoring following crops in those fields to make sure no volunteers emerge. In cereal crops, treating with a hormone herbicide is the best option for control.

In areas where you temporarily store beet, consider leaving this area uncropped so it’s easier to see any bolters emerge, and treat with glyphosate as soon as you see any.

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Alternator® Met, Cadou® Met and Octavian® Met contain diflufenican, flufenacet and metribuzin. Liberator® contains diflufenican and flufenacet. Proclus® contains aclonifen. Roundup® contains glyphosate. Alternator®, Cadou®, Conviso®, 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