Chemical Control Overiew
29 May 2019
It is now widely accepted that over-reliance on herbicides has led to the resistance issues we now face in the UK. That being said, it is still one of the most vital managing black-grass. When used with effective cultural controls, the right herbicide can make a huge difference to the success of your black-grass strategy.
High population levels and resistance to post-em graminicides means that both chemical and cultural control techniques need to be used together in order to gain acceptable levels of black-grass control.
Chemical control should start with the use of glyphosate on stubbles, stale seedbeds or cultivated soils to ‘burn-off’ any emerged black-grass prior to drilling the crop. Currently there are no confirmed cases of glyphosate resistant black-grass in the UK and it is important to follow WRAG guidelines to prevent it occurring (ref: Guidelines for minimising the risk of glyphosate resistance in the UK, WRAG 2016).
Once the crop is sown, the use of sequential applications of pre, peri and post-emergence herbicide mixtures is key to managing black-grass populations. Single applications made either pre or post-emergence are unlikely to give satisfactory control due to the nature of the weed, its germination pattern and strong, competitive growth.
Black-grass resistance to post-emergence graminicides is widespread resulting in the reduction in efficacy of these sprays. This means that we have to rely on the efficacy and get the most out of the residual herbicides which are applied pre and peri-emergence of the weed in order to gain control of black-grass.
Flufenacet and pendimethalin are currently the strongest pre-emergence active ingredients against black-grass and so products that contain these actives tend to give the best levels of control.
BASF and independent trials over several years have shown that pre-em applications of Crystal, which contains flufenacet and pendimethalin, in mixture with DFF gives the best start to black-grass control. For the most challenging black-grass situations use a pre-em programme of Avadex granules followed by Crystal + DFF at full rates 4.0lt/ha of Crystal and 0.2lt/ha DFF.
Once the crop starts to emerge, products containing flufenacet and pendimethalin, such as Crystal, Pontos and Quirinus are also valuable partners in the early follow-up herbicide application timing when the black-grass is at peri-em or very early post-em. This sequence of applications effectively ‘tops up’ the pre-em sprays in order to obtain the greatest persistency and control of the black-grass.