Last week's cold and wet snap has probably closed the window for Atlantis (iodosulfuron-methyl-sodium + mesosulfuron-methyl) applications pre-Christmas, Ben Giles of Bayer CropScience admits.

Sunny, dry weather has been in short supply for growers wanting to apply post-emergence blackgrass sprays this autumn

"The issue is more the ground conditions than the cold," he says. "It is too wet to travel and the crop is probably more stressed from sitting in saturated soils than the cold weather.

"In 95% of cases that probably means growers will be packing up the sprayer for Christmas now."

If ground conditions do improve before the new year there might be a small proportion of crops that would benefit from a spray, he notes. "In one or two cases where nothing has been applied yet this autumn it might be worth spraying."

But most growers would likely be applying propyzamide to oilseed rape as a first choice if conditions improved.

He estimates no more than 5% of Atlantis applications have been this autumn. "Blackgrass is an awful lot smaller, and pre-emergence sprays appear to have worked well, so I totally sympathise with people not spraying."

The only applications that have been made are generally where a pre-emergence spray had not been applied and a carpet of blackgrass had come through, he says.

In the new year it is important, particularly if December and January are cold, not to rush on with Atlantis at the first sign of better conditions, he says. "You're looking for a reasonably prolonged period that allows active growth [for Atlantis to work most effectively]. If those conditions happen in February or early March then great, but two days above 6C is not going to do it."

Rushing out on the first "half-decent" day in February, if conditions are not right, could result in poorer control based on previous year's evidence, he warns.