Fresh blackgrass approach needed

BLACKGRASS IS getting the better of arable farmers despite their best efforts, according to latest survey results.

More than half of the land in Syngenta‘s nationwide survey of 252 growers covering over 60,000ha (150,000 acres), was infested with the weed.

The survey also showed that 81% of blackgrass populations are now considered ‘bad‘ or ‘resistant‘, up from 49% in a similar survey five years ago.

Fortunately greater awareness is spurring growers to fight back with a wide range of tactics, said the firm‘s Alison Bosher.

“The message seems to be getting through that you can‘t rely on chemical control.”

But, there is still room for improvement, said Miss Bosher.

Post-emergence sprays need to go on earlier at the “unfolded paper clip” one-two leaf stage, rather than the two-three leaf stage, she said.

Delaying risks some plants reaching the much-harder-to-control tillering stage.

Increased blackgrass dormancy this year means germination is likely to spread over a longer period than normal making robust post-em control extra important, added the firm‘s Iain Hamilton.

“By adding extra contact plus residual activity you can improve on that variability.”

He recommended using Hawk (clodinafop-propargyl + trifluralin) early post-em, along with the new recommendation of 3 litres/ha of isoproturon (up from 2 litres last year).