SIGNIFICANT INCREASES in grass weed infestations led to a marked rise in the use of in-crop herbicides over the past year, according to a new study.

Blackgrass and brome were identified as the biggest weed threats, by 100 Masstock Arable Group participating agronomists.

Significantly, 97% reported increased in-crop herbicide use in 2003/04.

“Over 60% of our team saw increased weed problems invariably or generally associated with either ineffective stale seedbeds or minimum tillage,” said study co-ordinator Clare Bend.

“Just under half, reported a clear association with herbicide resistant weeds.”

Weed control strategies for the coming season will focus on better control outside the growing crop, she added.

“Compared with in-crop solutions, these involve fewer compromises with the needs of the growing crop, raise no resistance issues, and offer substantial cost savings.”

Masstock‘s favoured option is delayed drilling, giving more pre-planting weed control opportunities.

Other options include pre-harvest herbicide treatments, better stale seedbed and pre-emergence herbicide use and replacing second wheats with oilseed rape.

“We are not advocating a wholesale move out of early drilling, just a more considered approach when deciding which fields to drill first.

“Fields with a real grassweed problem shouldn‘t be drilled before the 4th week of September.”

“Grass weed control has to be about managing populations with every agronomic and rotational as well as agrochemical means available,” she concluded.