West: Warm weather boost for OSR needed

Autumn fieldwork is proceeding well. Some growers have already finished drilling, some are yet to start.

There have been good conditions for false seedbeds to do their work, with occasional showers to keep the soil moist and producing a useful flush of brome and blackgrass, to be killed with glyphosate.

Oilseed rape has established well but is growing only slowly. It’s difficult to see why, as the soil is warm and growth should be more rapid. Perhaps after the rain of this weekend and a warmer week to come, growth will accelerate. It’s not too late to apply a small dose of nitrogen to crops if you feel it would help.

So far I have seen no symptoms of phoma but all crops need to be checked carefully, especially the more susceptible varieties. The risk of subsequent stem canker next summer is greater if phoma lesions develop on a small plant, so if phoma is found at this early stage, apply a fungicide as soon as possible.

Volunteer cereals and blackgrass seedlings in rape are now at the stage to be sprayed. Low rates of propaquizafop will be used on the volunteers but if there is a significant blackgrass infestation we shall switch to cycloxydim or tepraloxydim.

Winter cereals are being sprayed pre-emergence, particularly where there is risk of blackgrass. A flufenacet-based herbicide plus flupyrsulfuron methyl is the usual choice in barley, flufenacet plus DFF or prosulfocarb in wheat. There are only limited options for blackgrass control post-emergence in barley so it really is essential to take the pre-emergence route. 

Note that where pre-emergence herbicides are used, the seed should be covered by at least 32mm of soil after rolling. Crop thinning will occur if the seed is too shallow, especially if heavy rain follows spraying.

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