Applying Atlantis in the autumn rather than the spring would give growers better blackgrass control, save money on inputs and result in more yield, according to the results of this year’s Agrovista’s blackgrass trials at Maidwell, Northants.

As with many growers spring applications of Atlantis, on 22 March, had not worked as effectively as in the past.

But the poorer control, about 85-90% after a pre-emergence and holding spray, was not the result of resistance, Agrovista’s Mark Hemmant told Farmers Weekly in an exclusive tour.

“Many are worrying they have got resistance, but it is more of a timing issue.

It went on as we came out of a cold spell when the grassweeds weren’t growing very well.”

It was not just restricted to Atlantis, he added.

“Other sulfonylureas applied around that date for broadleaved weed control haven’t worked as well either.”

In contrast an Atlantis plus residual treatment applied in the autumn gave 100% control.

Correctly timed autumn sprays had proved to be more consistent over the past four years of trials with the product, he noted.

Commercially, Atlantis had been a victim of its own success in the spring, he said.

“Many insist on using it in the spring – there are a lot of excuses, wild oats, cleavers, etc.

But if you are serious about controlling blackgrass you need to use your best kit at the best time.”

Autumn applications would not only give the best control, but also protect yields and save money.

“Too many judge blackgrass control simply by heads, but yield is just as important.

It is as much about when you remove it as how much.”

Growers who planned to use Atlantis in the spring were gambling with the weather, he suggested.

“You’ve no idea what it will do.”

Last season’s trials at Maidwell illustrated the importance of early removal of blackgrass.

“The difference was around 0.5t/ha where Atlantis went on in the spring, including a holding spray, compared with an autumn spray.” Bayer trials put the difference at as much as 1t/ha, he added.

“But, not only that, by applying the Atlantis in the autumn you are going to save yourself the cost of having to apply the holding spray.”

The difference could be worth £10-20/ha depending on residual partner and holding spray.

This season both October and November applications of Atlantis had worked effectively, despite little emerged blackgrass at the time of the earlier application.

The result was surprising, Mr Hemmant admitted.

“In previous seasons October sprays have been too early.”

Agrovista’s preferred residual partner for Atlantis against blackgrass was Firebird, Mr Hemmant said.

“We are generally finding pendimethalin applied post-emergence isn’t doing what it used to because of enhanced metabolism [resistance].

So the place to use it is where it will be less susceptible to that – ie pre-emergence.”

In other Agrovista blackgrass trials Firebird had performed better than Stomp or trifluralin, he said, although each at this site gave 100% control.

mike.abram@rbi.co.uk