Blackgrass trials carried out by Masstock have proven the worth of a pre-emergence herbicide in winter wheat. The trials also suggest those growers who delayed control until spring will have suffered a significant yield loss.

Head counts have been taken for the trials at the Brackley SMARTfarm, Northamptonshire which looked at a range of herbicide strategies in winter wheat. Crystal (flufenacet + pendimethalin) was used pre-emergence followed by Trump (isoproturon + pendimethalin) or Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium).

“What's interesting is Crystal followed by Trump,” comments Masstock agronomist Andrew Richards, who has co-ordinated the trials. “The blackgrass headcount is relatively high, but the crop competition is lower. In terms of preserving yield, the pre-em is clearly doing its job.”

This contrasts with Trump followed by Atlantis in the spring. This left a high headcount of blackgrass, but the number of wheat ears in the plots were considerably lower.

None of the spring treatments of Atlantis performed very well, reports Mr Richards, with the best results coming where Crystal was followed by a well-timed Atlantis - applied in early December.

“The key points to remember are don't let the blackgrass grow too big and put Atlantis on while the weed is actively growing,” he advises. “You take a big gamble on the conditions being right if you leave your application until the spring. This year it was too cold when the Atlantis was applied on 19 March and the blackgrass was well tillered.”

Mr Richards' advice is to get on early with blackgrass control, especially if there is a high burden. “Start after harvest and try to take as much of the weed out with cultivations and glyphosate before drilling.

“Post-drilling, Crystal is a vital starting platform for blackgrass, but the crop needs to be drilled at a minimum depth of 32mm.”

A two-spray programme will be the only cost-effective option for most growers, since few growers have as much as £80-90/ha to spend on their blackgrass control. So Atlantis may be the best follow-up, advises Mr Richards. “But don't rely on it. Take out as much pre-emergence as you can and make sure your Atlantis goes on in the right conditions, or you'll get poor results. Remember, we have to look after this chemistry, because if resistance creeps in, there is nothing new in the pipeline to take its place.”