Key Points
- A herbicide trial was set up in a crop of spring sown oats near Gore to investigate the control of willow weed following reports of growers having difficulty controlling this weed.
- Saxon™ 3 l/ha (group O), Bromotril® 1.2 l/ha (Group C) and Trimec® 3.5 l/ha (Group O) gave complete control of willow weed.
- Both Granstar® and Glean®, which belong to the sulfonylurea herbicide mode of action (group B), performed poorly on willow weed at this site.
- It is possible that a biotype of willow weed with increased tolerance or resistance to group B herbicides has developed after many years of application of these herbicides.
- Willow weed seed was collected from the trial site and will go through formal resistance assessment.
- To slow the development of resistant weeds it is important to alternate herbicides from different modes of action (eg Group C and O) that are effective on the target weed species.