By Andrew Blake

 WARM WEATHER forecast for the weekend means growers are facing their last chance to tackle blackgrass in winter wheat before it is too big for effective control.

With some blackgrass already at stem extension, prompt treatment is a priority, warns TAG”s Beds-based David Parish.

Atlantis (iodosulfuron-methyl-sodium + mesosulfuron-methyl) is likely to be the product of choice, says Masstock”s Clare Bend. “Blackgrass is now at the mid-tillering stage, and once it gets beyond that it really starts to eat into yield. You can lose 0.3t/ha for every two weeks delay after that.”

Last season”s company trials showed that early tillering (GS22-23) application gave 100% control. Leaving treatment until the end of March – by which time the weed had six tillers – gave only 95% control, and delaying spraying until the end of tillering (GS29) in mid-April left 10% as escapees.

 To help growers this season Bayer has extended the cut-off date for Atlantis to Apr 15, says Barry Hunt of Atlantis-maker Bayer CropScience.

That is welcomed by Bob Mills of supplier Banks Cargill. “It provides a useful cushion.”

But unlike last year, when blackgrass was less advanced, this spring”s much larger plants escaping the generally good flufenacet-based autumn control are a real challenge. “That”s going to be quite a test.”

Where Atlantis cannot be used in time the trade may take product back, suggests Mr Mills. “We”d be sympathetic.”

 Although Atlantis is likely to be first choice for many growers, there is scope for other options, suggests Northants AICC member Malcolm Harrison.

“For those with less of a problem, and who have used a less sophisticated approach in the past, Lexus will do a magnificent job.”

andrew.blake@rbi.co.uk