Cereals 2009: Growers warned of ‘new’ weed

Be on the look out for a “new” weed in arable fields, particularly in min-till or direct drilled crops, Stephen Moss of Rothamsted Research warned at Cereals 2009.

Rat’s-tail fescue (Vulpia myuros) was cropping up in more arable fields, including three fields at Rothamsted, and was associated with non-inversion tillage, he said.

“Heads appear at the same time as blackgrass and our experience is that it can suddenly appear in fields as if from nowhere.

“The heads form a dense panicle with spikelets that look rather like Italian ryegrass but with longer awns. It can form dense patches, especially where crops are thin.”

Dr Moss was keen to hear from growers with dense patches of the weed. “I don’t want to over play the resistance card, but we do need to confirm whether resistance is an issue with this weed.

“If farmers find it confined to small patches, spraying off with glyphosate in late June or early July might be sensible.”

Rat’s-tail fescue had become a serious problem in the USA, and had also become established in Denmark where research had shown it was associated with reduced tillage.

Trials in the USA suggested that flufenacet-based products could give good control, but the rates used were much higher than those approved in the UK. Post-emergence control was more variable with sulfosulfuron (as in Monitor) giving slightly better control than mesosulfuron (as in Atlantis), although again not at UK rates, he reported.

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