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Crop Advice & Expertise

What’s happening in fields in the South East this October?

Oilseed rape crops are reaching the Phoma treatment threshold on Nick Lewis’s patch and he’s also weighing up pre-emergence herbicide strategies in wheat this autumn

At a Glance

This month’s update includes information on:

  • Disease control strategies in oilseed rape
  • Pre-emergence herbicide choice in wheat
  • Slug control in winter cereals





Oilseed rape

The oilseed rape area has remained stable this autumn. If anything, there might be a slight uplift where growers moved away from the crop have now decided to give it another go.

Overall, we have some very large plants where crops were drilled early, as most went into a good quality seedbeds with plenty of moisture during the optimum window. These larger, early-sown crops will need an autumn plant growth regulator, which can be applied as a standalone application or combined with a Phoma spray.

Most crops aren’t quite at the 10% of plants infected threshold yet for Phoma, but I’ve seen fields in Hampshire that are almost there. The pressure will move eastwards towards Kent over the next week to 10 days and as soon as thresholds are reached, a fungicide treatment should be applied.

You get a significant yield response from an autumn fungicide, so it makes it worthwhile to choose the best azole active – prothioconazole – that covers both Phoma and light leaf spot. It’s possible that you might not be able to travel to apply a follow up light leaf spot spray, so it is crucial to get protection against both diseases in the first hit.

There is a lot of turnip sawfly in the area this year and it’s worth monitoring. While there isn’t any specific treatment for turnip sawfly, you might get some incidental control when using an insecticide such as Biscaya (thiacloprid) for aphid control.

Turnip Sawfly



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Across the region growers are about 40% through cereal drilling now. Where there is bad black-grass people are generally holding off. Seedbed conditions have been relatively good so far, but where they are less than ideal it’s a good idea to hold off and let soils weather down further. This will help the efficacy of pre-emergence herbicides.

Pre-ems should be applied straight after wheat drilling and the cornerstone of black-grass control remains Liberator (flufenacet + diflufenican), while ryegrass – which is a problem in this area – would benefit from prosulfocarb and/or tri-allate in the stack. Flurtamone also adds some useful activity.

It is crucial to mix modes of action as part of an anti-resistance strategy. Where resistance might be an issue with actives such as pendimethalin, ensure there are products in the tank that cover any gaps in control.

Liberator plus Defy (prosulfocarb), followed by Avadex (tri-allate) at peri-emergence has been effective and growers should ensure the products are going on in good, moist seedbed conditions. Also, spray in suitable conditions and do your best to reduce drift.

Slugs haven’t been as much of an issue as first feared after the wet weather, but remain vigilant and treat where necessary. Be aware of metaldehyde stewardship guidelines and don’t forget ferric phosphate – it’s an equally effective product, with fewer restrictions.