Late applications of Atlantis gave strong but delayed response

Agronomists have allayed worries about the effectiveness of Atlantis WG (mesosulfuron and iodosulfuron) treatments applied before December’s cold weather.

Apparently healthy-looking black-grass on sites throughout the country in January had raised concerns about Atlantis’ effectiveness, but recent warmer temperatures have now brought on a strong - if somewhat delayed - response.

’I was concerned for a short while,’ says independent agronomist Andrew Cotton. ’As temperatures dropped, the black-grass simply became dormant. But there was sufficient uptake in those couple of days between application and the weather turning to allow the actives to do their job.’

Masstock agronomist Tim Horton had a similar experience. ’Quite a few treatments went on in very late November, only three or four days before that cold weather,’ he says. ’Six weeks went by before it was displaying symptoms, but in most places, control with Atlantis has been good to very good which is in contrast to last year.

’In areas where there are very high populations, 98% control still leaves a reasonable amount of survivors. Here we will look at cultural methods of control such as a change in cropping, choosing more competitive varieties and stale seed beds - these worked really well last autumn.’

Bayer CropScience trials sites which received Atlantis WG and a residual partner in December were also showing few signs of activity as they emerged from the snow. But during the last month, as temperatures have risen, the black-grass has died.

’Applications from the third week of November have been the most affected as a fortnight of very cold weather followed,’ says Ben Giles, commercial technical manager at Bayer CropScience. ’Product uptake by the black-grass would have occurred in that first short window but the majority of the activity has only been seen since soils warmed up.

’The snow insulated most black-grass from the worst of the weather with the pre-ems working beneath the blanket. The vast majority of fields have come out a lot cleaner than they were in the autumn.

’In cases where there has still been no activity from these pre-Christmas applications, growers should be prepared to investigate further to see whether there’s another underlying cause’, he advises.