Trifluralin replacements trialled for blackgrass control

Trifluralin will be missed more in blackgrass programmes than IPU, and whatever it is replaced with will mean growers “shelling out more money,” according to The Arable Group‘s Jim Orson said.

As a partner for Atlantis, trifluralin had proved very useful, Bayer’s Tim Holt said. “It was cheap and there was no blackgrass resistance to it. I think it helped keep some of the pressure off Atlantis.”

Bayer was searching for alternative partners, but in the short term the only option was pendimethalin, he suggested. Other possible partners including flufenacet / DFF-based treatments were, however, being investigated.

The role for an Atlantis partner was becoming increasingly important, Mr Orson said. “Up until recently we were not getting extra control from a partner, but the last couple of years we are seeing more control where Atlantis performance has started to slip. The issue is finding a range of materials to mix.”

trifluralin sprayer

He advocated growers applied Atlantis almost regardless of blackgrass growth stage at the end of October into very early November for September-sown wheat. “I think the current recommendation for 2-3 leaf blackgrass is too cautious. You have good growing conditions then, and blackgrass is largely up by the middle of November.

“It also has the advantage of putting on the partner product when it is likely to have its best effect – the smaller the plant the better.”

Last year only 10% of Atlantis was used in the autumn, Bayer’s Gilles Chevallier admitted. “That was very disappointing.”

Part of that was due to the season, Peter Riley of Prime Agriculture said. “Residuals were working well and we had a wet and cold November that delayed spraying.”

Fears over high dormancy delaying germination could have been another factor, but Mr Orson stressed growers should use that information only to time drilling and not spraying.

“Getting Atlantis applications right in the spring can be very marginal,” he added. “They generally worked well in early April this year, but by then you’ve lost yield. And if people say there isn’t a yield penalty because blackgrass population is low, then why use Atlantis? They should be looking at alternatives

“It has always been warm enough to get results with Atlantis in early November regardless of size, and you will get season-long control as long as you use a pre-emergence and partner product with Atlantis.”

A Liberator plus Defy mix is an option both Bayer and Syngenta have looked at for replacing trifluralin in mix with both products. But the two firms disagree about the optimum rates of each in the mix. While Syngenta is recommending 4.0 litres/ha of Defy plus 0.3-0.4 litres/ha of Liberator (see FW 11 July 2008, Arable, p56) Mr Holt suggested 0.6 litres/ha of Liberator plus 2.0 litres/ha of Defy.

“Our trials showed up to 6% increase in blackgrass control with this mix compared with Liberator at 0.6 litres/ha.”

But the mixture of 4.0 litres/ha Defy plus 0.3 litres/ha Liberator gave 10% less control in the Bayer trial, compared with the Liberator alone, which was why Bayer would not be backing the mix at those rates, Mr Holt said. “Defy is useful because it adds another mode of action into the programme, but you need the high rate of Liberator.”

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