What to do before closing the gate on arable fields in Scotland

Weed control options for drilled cereals 

If drilling has gone well in September, the remaining fields of wheat might be mostly those after potatoes. It would also be positive if they had mostly been rolled and sprayed with a pre-emergence herbicide. 

In that case top up herbicides might be needed if you have difficult broadleaf weeds to control, such as bur chervil and groundsel, which is where our metribuzin-based products can be used. These also contain flufenacet and diflufenican, with the metribuzin adding some contact activity.  

They have a fairly wide window for application – up to GS25 of the crop – but ideally you want the weeds to be growing and treating while relatively small.  

With also increasing problems with some sulfonyurea-resistant weeds, such as chickweed and poppy, using the MET products in the autumn can help avoid using the same group of chemistry year-on-year to control the same weeds. 

If you have issues with difficult grass-weeds, such as bromes or black-grass. Mesosulfuron-based contact herbicides are also an option post emergence, but I’d suggest the MET products first as a top up of flufenacet, especially after heavy rain and leave the mesosulfuron-based ones, if needed, for later.     

Options for later drilled wheat 

Where wheat drilling carries on into October, a pre-emergence herbicide will give the best start for weed control, especially where fields have difficult grass-weed pressures.  

Options in that case include Liberator (flufenacet + diflufenican) + Proclus (aclonifen) where pressure from brome or Italian ryegrass is high, while prosulfocarb or tri-allate with Liberator are alternative options.  

If weed pressure is annual meadowgrass and broadleaf weeds, then there’s more of a choice of pre- or post-emergence, but I favour pre-emergence as it gives a good foundation of weed control and removes the risk of not getting on as we saw last year and allows for more modes of action within the programme, helping reduce resistance development.  

In these fields, the MET products again are an alternative option to higher doses of Liberator.  

Monitor for light leaf spot and pests in oilseed rape 

With oilseed rape crops off to a great start, it’s worth starting to monitor for light leaf spot during October. It’s easy to do by picking a few leaves and placing in a bag in the airing cupboard to incubate and then looking for symptoms a few days later which weren’t visible at the time of sampling. 

Fields close to last year’s oilseed rape can be particularly at risk from the early development of light leaf spot. 

If crops do need treating, then a product like Aviator (bixafen + prothioconazole) can have a dual benefit in also helping with greening and building root mass, keeping the plant healthy, as well as the disease control.  

The other thing to monitor for is rape winter stem weevil, which is becoming a bigger problem in Scotland. It’s not that easy to spot in autumn, but the larvae can have a really big impact on yield after causing stunted growth and multiple branching from the plant base.   Adding Decis protech to a fungicide spray, if necessary, would provide some control.     

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