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Spring Barley: Weed control – May 2020

13 May 2020

Annual meadow-grass is not particularly competitive in spring barley, but it can be a serious nuisance at harvest, particularly in a wet harvest.

Also, it can produce as many as 2000 seeds per plant, and dormancy is quite low so many of the seeds germinate in following crops.  Annual meadow-grass significantly reduces the yield of grass swards, so if the field is likely to be in the grass in the next few years, it is worthwhile controlling in spring barley to limit seed return to the soil.

There are many combinations of broad-spectrum post-emergence broad-leaved weed herbicides available, some examples of treatments are given below. Generally, the herbicides are best applied early to small weeds.  This gives the best yield response. However care is needed with synthetic auxin based products, particularly the older ones – MCPA and dicamba, for instance, can’t be applied before the crop 5 leaf stage, distorted ears are likely if applied too early.

Most spring barley broad-leaved weed control is based around a sulfonylurea (SU). They tend to be very good on chickweed, mayweeds, hemp (day)-nettles, charlock and amsinckia/bugloss-type weeds. However, resistance in weeds such as scentless mayweed, chickweed and poppy is increasingly common so SUs are recommended with a tank-mix partner, usually a synthetic auxin. In cases where resistance is a major issue, it is probably best to steer clear of SUs.

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