SERIOUS BROME infestations more than doubled last year, according to ProCam Agronomy, confirming the firm’s worst fears at the start of the season.

Its field-by-field 4cast analysis taken from over 400,000ha (1m acres) of UK cropping shows a 100% year-on-year rise in the amount of wheat treated with a spring brome herbicide in 2004.

And agronomists suggest this almost certainly under-estimates the scale of the problem. “Our recording system shows 14% of wheat crops were treated with either Monitor or Ethos last spring,” says ProCam’s Nick Myers. This compares with just 7% in 2003.

“At the same time, we know national supply limitations meant not all the 2004 recommended treatments could be applied.

“Many less serious infestations in particular went untreated. So the actual incidence last season was undoubtedly higher than our records show.”

While Mr Myers regards the increase as worrying, he is by no means surprised, having seen a steady build-up in recent years and knowing how easily brome populations can mushroom.

Indeed, last February he and his colleagues publicly warned of the likelihood of a big upsurge in infestations. In particular, they highlighted the rise minimum tillage, several years of poor stale seed-beds and a population shift away from barren brome to a more mixed spectrum of species.

“Decent soil moisture for the first time in three seasons meant good grass weed seed germination ahead of cereal drilling last autumn,” he says.

“But many people found it too wet to achieve more than a single stale seed-bed dose of Roundup which, in most cases, will have been insufficient to really knock back the brome seed reservoir.”

More extensive use of Atlantis may have helped reduce the extent to which autumn weed controls previously helped brome by eliminating competing weeds like blackgrass, he believes.

“However, we have found it gives highly variable brome control. And the persistent wet weather played havoc with many post-em programmes.”

andrew.blake@rbi.co.uk