Early removal of wild oats is key to protecting spring barley yields – producing a cleaner crop and helping to optimise crop margins, say agronomists.
Growers should use pre-emergence residual herbicides to tackle expected wild oat populations before they emerge – following the same path as for winter crops, suggests Gowan herbicide technical lead Will Smith.
“Post-emergence herbicides are no longer quite as effective, whether through resistance or inconsistency around application technique or weather, making it difficult to hit the target weed with the active substance.”
Pre-emergence residual products, however, carry their own risks. Most rely on soil moisture, which is less reliable in spring. “It’s why the performance of products in the autumn isn’t necessarily replicated in spring conditions due to drier seedbeds.”
Exception
Avadex (tri-allate) is an exception. It works partly through a gaseous phase rather than relying solely on moisture. “That gives higher relative efficacy in dry conditions compared with other actives,” Dr Smith says.
The product can be applied before drilling spring barley, including alongside glyphosate, and incorporated by cultivation or the drill. “In drier conditions, that can help maintain effectiveness.”
While blackgrass and Italian ryegrass remain important targets, wild oats cause the greatest yield loss, even at low levels. “They are one of the most competitive weeds and so have a more direct impact on yield in season than other weeds.”
That makes early control essential. “By removing them pre-emergence, they never have the opportunity to compete with the crop, whereas if you wait 4-6 weeks until the wild oats are 2-3 leaves, even at that young stage, our trials have shown you can be losing as much as 15% in yield.”
Avadex is particularly effective on wild oats, offering value through Avadex Excel or the liquid formulation Avadex Factor, says Dr Smith.
“Wild oat germination is notoriously unpredictable and often elongated but using Avadex at the beginning of the programme can reduce or remove the need for any follow-up treatment, which in a busy period in the season can be invaluable.”
In the field
Rutland-based independent agronomist Ben Mead of Smart-Ag typically uses pre-emergence sprays in spring barley, depending on drilling date. “Where it has been established in February or up to around the middle of March, as long as we have moisture, there’s a benefit from using a pre-emergence.”
Mr Mead says his main grassweed target is blackgrass, which he says becomes harder to control later in the spring. “Applying residual herbicide onto a drying or dry soil doesn’t get the best out of it.”
For wild oats, Mr Mead uses Avadex, particularly where ACCase resistance is known, or a post-emergence ACCase treatment such as pinoxaden or fenoxaprop-P-ethyl.
“Avadex is better than anything else pre-emergence on wild oats,” he says. “I’ve usually followed up with a post-emergence, but it helps reduce the population.”