Managing Herbicide Resistant Wild Oats

and removed the material to prevent adding herbicideresistant wild oat seed to the weed seed bank.

Wild oat resistance to Group 1 and Group 2 herbicides in Peace Region is increasing. Poorly competitive crops due to extreme weather amplify the issue. In 2020, SARDA Ag Research identified a uniform area of wild oats resistant to Puma Advance. Sample seed collected from the patch showed 97% resistance to Puma Advance (fenoxaprop-ethyl), 31% resistant to Axial (pinoxaden) and 5% resistant to Centurion (clethodim). While this is not good, it allowed SARDA Ag Research to demonstrate different options to control herbicide-resistant wild oats.

SARDA Ag Research staff staked 2m X 8m plots using a Randomized Complete Block (RCB) design with four replications. Pre-seed and in-crop wild oat herbicides were applied with a 2m hand-held boom. During the season, staff took visual wild oat ratings. Following numerous ratings, staff cut the wheat early

Pre-seed treatments were applied May 6 following label recommendations. Staff seeded wheat on May 7 over the entire demonstration area. Three in-crop herbicide applications were used on June 11 when the wild oats were at the 2-5 leaf stage.

Pre-seed Herbicide Treatments

All pre-seed herbicides provided some suppression/control of wild oats. The effectiveness of pre-seed products on wild oats was Avadex>Focus>Fierce>Olympus. The degree of wild oat control with these products will vary depending on precipitation following application, soil type, crop residue in the field, application rates and water volumes.

In-crop herbicide applications of Everest provided reasonable control of wild oats. Axial provided some control, and Puma Advance did not provide any control. The results collected from the in-crop herbicide application were similar to “Herbicide Resistance Assay Results” on wild oat seeds collected from the demonstration area in 2020.

If you suspect a field has herbicide-resistant wild oats, collect seeds and send them to a lab to determine if and what herbicides they may resist. Incorporate multiple weed management strategies to reduce wild oat populations effectively. Wild oats are not the only weeds developing herbicide resistance. Other weeds, such as annual sowthistle, chickweed, common groundsel, stinkweed, shepherd’s purse, and kochia, which are all present in the Peace Region, are documented as being able to develope herbicide resistance. While these herbicide-resistant populations may not be present in the Peace Region, it is vital to use multiple strategies to control weeds and protect the effectiveness of herbicides.

Strategies to manage herbicide-resistant weeds:

• use different groups of pre-seed and in-crop herbicides to manage or prevent herbicideresistant weeds in annual crops.

• prevent all weeds from dispersing viable seeds.

• use diverse crop rotations,

• use higher seeding rates to increase the competitiveness of the crop,

• choose competitive crops,

• Sow later to allow control of early weed flushes,

• cut annual crops for green feed or silage, and

• incorporate perennial forages into crop rotations.