Getting the basics right for blackgrass control might mean avoiding using Atlantis – or at least minimising resistance build-up to the product, ADAS’s James Clarke said.

Growers with blackgrass problems needed to go back to basics and do everything possible to avoid using Atlantis, according to weed scientist James Clarke.

“That way, if you do need to use Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium) you’ll have done everything possible to avoid encouraging resistance,” Mr Clarke told visitors to ADAS Boxworth’s open day.

Resistance was no idle threat, he stressed. “We know there are at least 80 farms with confirmed Atlantis resistance and we think most of them have target-site resistance.”

Coupled with resistance was the loss of alternative herbicides, isoproturon and trifluralin. “There are no new herbicides coming through and we’re losing the ones we have got, either through water quality concerns or resistance.

“We need to go back to basics,” Mr Clarke said, which meant a combination of getting good control in break crops, using the right cultivation tools, drilling later and using chemical control.

Continued or poorly thought-out shallow cultivations encouraged blackgrass, Mr Clarke said. “But there is nothing wrong with using them in the right context. You’ve got to think where your weeds are coming from. If you’ve got a really clean crop it’s better to use shallow cultivations rather than ploughing up buried seed.”

Growers also needed to think carefully about drilling date – or at least drilling order. “Think about which fields to drill last – there always has to be a last one. Why not make it your worst one for blackgrass?” he asked.

“Also, push those fields to the boundaries in your comfort zone (by drilling them as late as possible),” he said.

Chemically, the most important spray was now a pre-emergence. “It doesn’t really matter which product, as long as you hit the blackgrass hard and early.”

Mr Clarke urged growers to consider whether it was more important to apply a pre-emergence or to continue drilling, implying the former would be preferable.

Timing was important, if you did need to apply Atlantis. ADAS Boxworth trials showed applying pre-Christmas was more effective. But Mr Clarke was concerned that apparently clean crops could be masking Atlantis survivors below crop level. “Ensure you go into the crop and part it to check for survivors. There can be only two reasons why plants are there – they have emerged after spraying or have survived it. Knowing could give you an early warning of future problems,” said Mr Clarke.

Growers with resistance concerns can get seed tested as part of a Link project. “The test isn’t as advanced as for other chemicals but it is worth offering,” Mr Clarke said.

Blackgrass Control
  • Resistance to Atlantis concerns
  • IPU/trifluralin withdrawal
  • Need to do basics
  • Cultural controls crucial
  • Pre-emergence essential

mike.abram@bi.co.uk