West: Need to maintain focus on blackgrass control

Crop yield potentials have been raised by welcome warm rain at the end of May – particularly on some of the spring sown crops, which had a difficult start.

Most winter wheat flag leaf fungicide mixes have now been applied. We hope that these expensive disease control programmes, which started in March, will provide a good return this year, as yellow rust and septoria are easily visible and are very active on any missed areas. The earlier than usual emergence of flag leaves means that a follow up treatment at ear emergence will be essential. The recent rainfall will allow efficient use of late applied nitrogen.

Winter barley and oats look well. Growth regulators have been applied, and we won’t know till later whether higher rates should have been used – it’s always a difficult balance as most growers of these crops do require a good straw yield.

Spring cereals now look full of promise and herbicide and fungicide treatments are being applied as the crops close in. The variable costs associated with spring cereals are significantly lower than for winter crops.

The spring break crops have improved rapidly, with large flushes of weeds now needing treatment particularly in linseed and maize. Pre-emergence herbicides in spring beans have worked well.

It will be no surprise that the only bad news is the brown haze of blackgrass ears appearing in some wheat crops all over the main arable growing areas of the country – despite a small fortune being spent on both pre- and post-emergence herbicides. The end of May is always a day of reckoning – and this coming season may require further changes in cropping policy.

Changes to the rotation and inclusion of some spring cropping have been major factors in keeping on top of the blackgrass problem. It is concerning that some blackgrass has survived in winter rape even with a sequence of three residual herbicide applications.

Over 97% control of blackgrass is needed each season in minimum or zero disturbance systems to maintain the status quo. This season we have had better than average control with autumn residuals and follow up post-emergence treatments. Even so, the required high level of control is not easily achieved in rotations based on early sown autumn crops. So more spring cropping – although maybe unpopular – looks inevitable, and second year winter wheats in particular could be even more difficult to keep clean in the future.



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