Capitalise on a strong start for grass weed control

Part article taken from Agronomist & Arable Farmer, February 2017

Weed control in cereals has got off to a strong start, but recent experience shows that this season’s battle is far from won. We discover how growers can gain the upper hand.

At this stage last season, many of us were pleased with a good drilling and herbicide campaign in the autumn and some healthy-looking crops. For black-grass control, there was a sense of optimism.

Unfortunately, cool, wet weather persisted through March and April, which hindered crop development and spray applications while allowing relatively few black grass plants to tiller extensively and produce numerous large heads, laden with seeds.

But conditions have been different this year; October and December were both very dry while there have been several more frosts than last winter - all of which point to a greater likelihood of the good start being converted into a good finish.

Late drilling rewarded

The differences between strategies for each season are particularly marked in the North, as Chris Martin, of Agrovista, notes.

""Last season many late sown crops struggled to establish, and furthermore, appeared to have less vigour to compete against grass weeds in the spring," he commented. ""Some growers have been tempted not to significantly delay drilling and pressed on during the seemingly perfect drilling window towards the end of September.""

The decision appears to have been a mistake, Mr Martin added, as many crops sown in September in bad grassy fields are struggling. He said: ""It was particularly dry at this period and residuals did not perform well on either black­ grass or ryegrass. While there was plenty of moisture just below the surface in the weed germination zone, the surface was incredibly dry, inhibiting residual herbicide performance.

""The only option in some of these fields may now be glyphosate and spring cropping.""

According to Mr Martin, the majority of those with grass weed problems did delay drilling into October.

Rain helped pre-emergence herbicides to work effectively soon after  applications. Many of these have been topped up with an additional residual at peri-emergence and are looking relatively clean of both grass and broad-leaved weeds. Nevertheless, in areas with problem black­ grass or ryegrass, an Atlantis (mesosulfuron + iodosulfuron) type product will probably be used in early spring, unless target site resistance is confirmed on the field.