Pre-ems are crucial for tackling tricky weed threat

Pre-emergence herbicides will be essential this autumn if growers are to get on top of protracted and variable weed germination, ProCam has advised.

Both blackgrass and ryegrass will probably take longer to emerge and relying on a single spray of Atlantis (iodosulfuron + mesosulfuron) or other post-emergence options is likely to be less effective, technical director David Ellerton said.

Weeds could continue to germinate after autumn applications – possibly into February, as occurred in 2004.

But waiting until spring meant products might be less effective if enhanced metabolism resistance was present and growers also risked a reduction in yield due to weed competition, he said.

A robust pre-emergence herbicide reduced the initial weed burden and provided insurance against the lack of a post-em spray window.

“To optimise the benefit of pre-em herbicides, growers should utilise as many modes of action as possible to help increase chances of success, including trifluralin, pendimethalin, flufenacet and prosulfocarb,” Dr Ellerton suggested.

The revocation of IPU also meant low doses of pre-em product would become a major component of meadowgrass control strategies, he noted. “Without doubt this will be a year of yet another increase of pre-emergence programmes in a range of cereal weed control scenarios.”

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