Growers are being urged not to hold back on Atlantis applications this autumn, as residual herbicides struggle to control blackgrass in the dry conditions.
“Pre-emergence herbicides have not worked as well as last year and in situations where blackgrass is appearing in numbers people are very concerned about how much control they are going to get,” said Mark Hemmant, technical manager at Agrovista.
On top of this, the lower blackgrass dormancy has meant that fewer were taken out in stale seed-beds prior to drilling.
“Consequently, there is a much bigger need to spray Atlantis (iodosulfuron + mesosulfuron) in the autumn than there has been for a while. If the weather stays mild, you would expect more than normal to be sprayed.”
There are widespread reports of patchy crops in some regions due to drought. In some situations, crops have yet to emerge, but the blackgrass has. As a result, some growers are holding off with Atlantis applications until they see a good, healthy crop, Mr Hemmant says.
But he considers that waiting until the spring to spray Atlantis is a bigger gamble as blackgrass plants are bigger and can be more difficult to control.
“In some years, spraying Atlantis in the spring can damage crops. Growers also talk of yield losses of 1-2t/ha, but I don’t think there have been any trials to confirm this,” he adds.
For optimum control of blackgrass, Bayer recommends applying Atlantis at the 1-3 leaf stage, when most plants have emerged. “The right time to spray is around Bonfire night, but that may not be right for everybody,” says Mr Hemmant.
“Drilling date, variety, soil type, regional differences in weather and emergence of both crop and blackgrass will dictate.”
Farmacy agronomist Mark Bellamy said: “If you have got a good healthy crop and blackgrass at the right stage, I would definitely recommend spraying Atlantis in the autumn,” he said.
“When leaving it until the spring, the blackgrass potentially becomes larger and harder to control,” he warns. “If we get a late, wet spring and the blackgrass keeps growing, you will struggle to control it.”