Broad-leaved Weed Resistance



The demise of many active ingredients including isoproturon and trifluralin in recent years has left fewer options for grass and broad-leaved weed (BLW) control in cereals. The lack of new herbicide modes of action, combined with a heavy reliance on sulphonylureas (e.g. Atlantis, Ally) in winter and spring cereals has led to the development of resistant ALS resistant black-grass and could potentially have also been inadvertently leading to a build-up of ALS resistance in BLWs.

Confirmed cases of broad-leaved weed resistance in the UK


In the UK confirmed cases of BLW resistance are relatively few, but BLW resistance is increasing year-on-year where weed control has relied upon the use of sulphonylureas.

AICC trials manager & Agronomist Mike Thompson has already had test results confirming broad-leaved weed resistance.

“The problem of BLW resistance is increasing year-on-year. Resistant poppy has arisen on farms growing spring barley where weed control has relied upon sulphonulurea chemistry almost exclusively. Resistant chickweed is also occurring on black land, particularly where Atlantis has been used for black-grass control and sulphonylureas for BLW control”

Farmacy Agronomist Charles Wright carried out a survey of 150 agronomists in HL Hutchinsons – >30% of respondents suspected resistance.

“Some agronomists reported horrendous problems with poppies, especially in Lincs & Norfolk. Chickweed and mayweed were also a concern. Managing a resistant population is very different from black-grass – its like an on-off switch – one year control with ALS herbicides is good, then you get 1 or 2 mutations and before you know it they’re all resistant”

Reports of poor control are becoming more frequent and there is an increased risk now that ALS inhibitors can be used on most crops in the rotation. In spring crops sulphonylureas (ALS-inhibitors) are widely used, partly because there are fewer herbicide choices compared to autumn crops. It is important to avoid reliance on sulphonylureas for broad-leaved weed control (as this chemistry is high resistance risk) to prevent the same large scale resistance problems that exist today in black-grass. Take action now to ensure BLWs remain manageable.

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Weed control in cereals

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