TAG trials show early treatment boosts black-grass control

Spraying black-grass while still at its 1 leaf stage – compared with even just waiting until it has 2-3 leaves – can substantially boost control, independent trial plots by The Arable Group (TAG) have confirmed.

Across three separate winter wheat trials in Suffolk, Bedfordshire and Lincolnshire, applying a first post-emergence herbicide mix of Hawk with flupyrsulfuron to 1 leaf black-grass repeatedly gave better control than when the same treatment was applied at 2-3 leaves. An identical pre-emergence herbicide had been used beforehand in each case

Indeed at the worst infested site, Ixworth in Suffolk, where untreated black-grass populations reached some 939 heads per square metre, while the 2-3 leaf application reduced head counts to 315 per square metre, the same mix applied less than a month earlier at 1 leaf reduced this to just 77.

This was despite herbicide resistance having previously been confirmed at the site. A similar pattern of better control from earlier application was seen in the other trials.

According to Andrew Creasy, TAG trial manager for the Ixworth site, improved control from the earlier of the two sprays is down to black-grass plants being at their most vulnerable stage. “You are getting them at that very best timing,” he adds.

Of all the post-emergence treatments, top control at two out of three sites came when Hawk with isoproturon was applied to black-grass at 1 leaf as a holding spray, and then followed up later with mesosulfuron plus iodosulfuron once the weed reached 2-3 leaves.

By applying this early Hawk holding spray it makes black-grass more manageable going through winter, Mr Creasy suggests.

“Programmes are the best way to control difficult black-grass and Hawk fits into that,” he adds. “I think that the trial did show that a holding spray would work.”