The wild oat is one of the most widely recognised weeds in Ireland’s tillage fields. If left unchecked, this predominantly spring-germinating self-pollinating weed can substantially reduce crop yields due to its competitiveness.
Control, which was largely hand-rogueing in the past (labour-intensive but effective if done properly), now increasingly relies on herbicides.
However, some growers report increasing control difficulties when using herbicides. Following up on these reports, Teagasc collected samples from six wild oat field populations that survived herbicide programmes. The samples were collected for herbicide resistance testing from cereal-dominated crop rotations in Wexford, Kilkenny and Cork in June 2019.
The seeds were grown in a glasshouse to the three- to four-leaf stage, before receiving an application of herbicide with dose rates ranging from 0.25 (1/4) to eight times the recommended label rates of group A herbicides.
These were pinoxaden (Axial), propaquizafop (Falcon) and cycloxydim (Stratos Ultra). Four of the six populations were resistant to Axial. Five of the six populations were resistant to Falcon, requiring between two and eight times the recommended rate for control. Four populations were resistant to Stratos Ultra, with one of those still growing when eight times the recommended rate was used.
In all of these cases, control in the field with these herbicides could not work. This is extremely serious for future control of wild oats on these farms and it is vital to eliminate these weeds, or at least to contain these resistant weeds to the fields where they were found.
These farmers and the entire tillage community need to develop integrated control strategies adapted for our production systems. A key element is to understand the grass weed control situation on Irish tillage farms.
An integrated pest management (IPM) approach is critical for grass weed control. IPM requires the use of multiple cultural/non-chemical control tactics as the first form of defence, which includes crop rotations, use of competitive crops, higher seed rates, sowing dates, crop establishment techniques, stale seedbeds, hand rogueing and machine hygiene, with the use of herbicides reserved for critical use only. Following this approach will give farmers the best chance for effective control in the future.
Teagasc needs input from growers, and the industry in general, to get an understanding of current practices to help develop improved management for the future.
Teagasc is asking readers to fill in a short online survey to assess awareness of herbicide-resistant weeds, as well as adoption of resistance management strategies. The link to the survey can be found in this article, on the Irish Farmers Journal online or on the Teagasc ECT web page (search: Teagasc ECT) or by scanning the QR code at the end of this article.
The information gathered will be used to develop weed control programmes which are adapted to our environment and are practical to implement.
The survey takes about 10 minutes to complete and is divided into two sections. The first section looks at general weed control and the second section focuses on farm planning around the potential loss of glyphosate.
The survey can be found here.