Better than Atlantis? If you’ve got brome, or larger grassweeds late in spring, new grassweed herbicide Pacifica will be, according to manufacturer Bayer CropScience.

But the need to take out blackgrass early to maintain yield should restrict its use to specific niche situations, say agronomists.

Pacifica has the same mesosulfuron-methyl + iodosulfuron-methyl-sodium active ingredient combination as Atlantis, but in a stronger 3:1 ratio, says Bayer’s Nick Duncan.

That, combined with a 500g/ha full label dose rate compared with Atlantis’ 400g/ha, strengthens Pacifica’s efficacy against key grassweeds, particularly brome.

“Fundamentally it is a brome-plus product and should be used where growers have brome and either large blackgrass, ryegrass or wild oats.”

But it shouldn’t be seen as a late season fire brigade treatment or a standalone weed control solution, he stresses.

The higher dose of the two active ingredients that Pacifica delivers adds reliability and consistency to brome control compared with Atlantis, according to Bayer technical manager Gordon Anderson-Taylor.

While growers will have seen good control in some situations from Atlantis, it will lose up to 20-30% in comparison with the consistent 80-85% control of brome from Pacifica, he says.

That benefit is also seen against the more difficult to control great and sterile brome species compared with brome-specific herbicides Monitor and Attribut, he adds.

It is not just against brome where the increased dose helps.

“We also see an advantage at later timings on blackgrass.”

But growers should aim to target their blackgrass control pre-stem extension to maximise yield because, although Pacifica may be a better product in terms of percentage control, leaving applications later will result in yield loss from weed competition.

Pacifica also controls ryegrass better than Atlantis, and wild oats more consistently than Topik and Cheetah in Bayer trials.

At full rate Pacifica doubles the amount of iodosulfuron-methyl-sodium growers apply with Atlantis, increasing both the spectrum and size of broadleaved weed that can be tackled.

The new stronger combination should be seen as broader spectrum version of Atlantis on grass and broadleaved weeds, says AICC agronomist Patrick Stephenson.

“I anticipate it will be used in very complex grass weed situations in a very niche market.”

Growers will likely to be tempted to use it where autumn treatments haven’t worked and in particularly dirty fields.

But if growers put too much pressure on it through late spring applications there could be a wide-scale breakdown in control, he warns.

“How the product is stewarded will be important in delaying resistance building up to sulfonylureas.”

Frontier’s Bob Mills envisages the greatest advantage of the increased active ingredient will likely be seen on bigger ryegrass and bromes.

“On blackgrass it won’t technically be a step forward.”

That is because most growers will plan to have their Atlantis on in good time, he explains.

“But if the weather conspires against spraying in the spring there may be situations where growers may be forced to use Pacifica.”

fwarable@rbi.co.uk