The recent explosion in crop and blackgrass growth is prompting a rethink on autumn Atlantis applications.

Sprayers are expected to swing into action over the next 10 days, despite earlier concern that conditions were too dry for crop and weed to be advanced enough.

Now that soils have had a wetting, blackgrass has been coming through fast and in huge numbers, reports Dick Neale, technical manager with Hutchinsons. “It’s taken everyone by surprise.”

He believes that the seed bank is responsible as high weed numbers in East Anglia bear no relation to seed return over the past two years.

“Strong weed flushes always follow extreme environmental conditions. It was very cold for a while last winter, then we had a prolonged drought in September and October. Both are known to break dormancy.”

Blackgrass is coming up from depth, giving the impression that pre-emergence treatments haven’t worked, Mr Neale says.

“Don’t panic. These weeds have been growing up from beneath the chemical layer. Give it time – there’s always a benefit from a pre-emergence application.”

Some of that blackgrass may never have been treated with Atlantis (iodosulfuron + mesosulfuron), he adds. “If it’s old seed, it won’t have encountered the herbicide. So control should be good.”

In Lincolnshire, independent agronomist Sean Sparling expects that 50-55% of the 3440ha of winter wheat in his care will be treated this autumn, provided the weather remains suitable.

“The worst fields have already been covered. But on heavier land, emergence has been slow and, as Atlantis is a one-hit fix, it must go on at the right time and in the right conditions.”

Soil temperatures are 8.5C and seed-beds are moist. “Those are good conditions for Atlantis and I would expect to have most of the fields sprayed by Christmas. But it is a weather-dependent operation, as it must go on to a dry leaf.”

Flufenacet-based pre-emergence treatments have mostly worked well. “The rain we’ve had in the last two weeks has helped. Sensitised blackgrass is controlled better by post-emergence sprays – it’s a case of kicking a man while he’s down.”

Mr Sparling calls the middle of next week D-Day. “The numbers through by then will be what you will get this autumn. It’s always better to treat small blackgrass, but the weather needs to be on your side.”

Further south, blackgrass is beginning to tiller in early-drilled wheat at Velcourt’s Vine Farm in Hertfordshire. It will be treated with Atlantis plus a residual partner imminently, reports manager Tim Whitehead.

“Unfortunately, the later emerging wheats won’t be far enough forward for an autumn application of Atlantis. They’re much more variable.”