Harvest wins in the west and how to tackle crop risks this September

Gareth’s agronomy tips for September

1) Hybrid vigour needed for September-sown oilseed rape

Obviously, the secret with oilseed rape is getting it past all the various pest pressures, but unfortunately there aren’t any silver bullets that guarantee success. Doing lots of little things can all add up to help though, which is where monitoring cabbage stem flea beetle pressure with Bayer’s MagicTrap comes in.

It’s easy to be a little sceptical about the value of monitoring for flea beetle – after all, most of them are resistant to pyrethroid insecticides, but monitoring potentially allows you to adapt your drilling date to avoid the main migration period.

Conversely if you are going to use a pyrethroid insecticide, ideally you would want to use it when the pressure is at its maximum, and you will know that if you are monitoring.

In the west, September-drilled oilseed rape is pretty common. If you are growing later-sown oilseed rape, then hybrid vigour is the key trait to look for in a variety. In perfect conditions, you might not see the benefit, but in more challenging conditions, which becomes more likely with later drillings, that’s the benefits of growing a vigorous hybrid become obvious.

2) Destroy green bridge for BYDV infections

With high aphid populations this spring and summer, managing volunteer cereals in fields to avoid creating a green bridge for barley yellow dwarf virus infections to jump into newly emerging cereal crops will be important this autumn, and especially where farmers have no insecticide policy.

Ideally, Roundup® applications should be at least a week to 10 days ahead of drilling to make the volunteers are dead. It is a compromise, though, as leaving that gap does create a window for grass weeds to emerge, particularly if soil is moved.

Whenever you use glyphosate, continue to pay attention to stewardship and best practice guidance. That extends past the correct dose at the correct timing for the correct weed species to also monitoring for survivors, and making sure that if there are any, that these are destroyed by mechanical means before applying another dose of glyphosate.

Formulation also plays a part in efficacy, especially if conditions become challenging – that’s when you will likely see bigger differences between formulations.

3) Early drilling likely means more inputs required

After the challenging wet autumn and winter last season, plus an early finish to harvest, it seems inconceivable that most growers won’t be looking to drill cereals in September this year, should weather be conducive.

There’s nothing wrong with that but be aware that it will probably mean higher Septoria pressure, more weeds and higher risk of BYDV, and probably locks you into a higher input spend.

On the plus side you should have a more competitive crop – everything in farming ultimately is a compromise. You can mitigate some risk at farm level – for example drill your worst fields for grass weeds last rather than trying to drill everything late.

It’s also important to have a mindset of drill, spray, drill, spray, rather than drill everything and then think about spraying, especially where you have grassweed pressures.

Where black grass and Italian ryegrass are concerns, building a pre-emergence application around Proclus® is a good option. It is less affected by dry conditions that some other products and works well in combination with one of our metribuzin-based co-formulations, such as Alternator® Met, Cadou® Met or Octavian® Met, or Liberator®. The addition of metribuzin helps add a little bit more activity and another mode of action for grassweed control and broadens the weed spectrum for broadleaf weeds.

Remember that most residual pre-emergence herbicides need at least 32mm of covering soil, but check labels as some, such as Avadex® Factor require 40mm, and ideally apply within 48 hours of drilling for most consistent results.

4) Low blight pressure but don’t be complacent

The lack of moisture for most of the summer has helped keep blight pressure in potatoes very low. But don’t be complacent as it could change quickly and tends to ramp up at the end of the season.

For crops heading into store, in particular, an application of Infinito® will help control foliar blight and protect against tuber blight at the end of the programme.

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Alternator® Met, Cadou® Met and Octavian® Met contain diflufenican, flufenacet and metribuzin. Avadex® contains triallate. Infinito® contains fluopicolide and propamocarb. Liberator® contains diflufenican and flufenacet. Proclus® contains aclonifen. Roundup® contains glyphosate.

Alternator®, Cadou®, Liberator®, Infinito®, Octavian®, Proclus® and Roundup® 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