Teagasc is currently offering an extremely relevant herbicide resistance testing service for tillage farmers.
With a break in the harvest, this is the last opportunity to inspect crops for uncontrolled weeds and to collect samples for herbicide resistance testing, if resistance is suspected.
It is imperative for tillage farmers to know if they have uncontrolled weeds in their crops this year.
Moreover, it is equally important to identify a logical reason for their presence.
Uncontrolled weeds might result from choosing the wrong herbicide, applying it at an insufficient rate or encountering issues during application.
However, if you cannot easily explain the presence of these weeds, it might indicate a herbicide resistance issue in the field.
All grassweeds should be treated with caution particularly blackgrass, brome species and Italian rye grass. Herbicide resistance testing is advised where these weeds are present.
In addition, the level of annual meadow grass in winter crops seems to be higher than normal this year.
Whether this is a symptom of the wet weather in 2023/2024 or an indication of a greater issue is difficult to determine at this stage, but it is strongly advised to test any uncontrolled annual meadow grass that was treated with a herbicide that claims control.
Herbicide resistance
Herbicide resistance is not confined to grass weeds; chickweed is increasing in abundance every year, in addition to poppy, corn marigold and speedwells.
Where these weeds, and others, are poorly controlled, herbicide resistance testing can provide you with essential information on how to put a control plan in place.
Testing will be carried out as a part of the Department of Agriculture, Food and the Marine (DAFM)-funded EVOLVE research project.
This information is invaluable if a resistance problem exists, but is also immensely important to the research project in mapping resistance evolution.
Recent testing by Teagasc of resistance-suspect grass weeds revealed a worrying situation – 60% of samples submitted were found to be resistant to a wide range of herbicides.
Italian ryegrass is a case in point. A total of 17 different populations were grown alongside a herbicide-sensitive control.
All were sprayed at the two to three-leaf stage with label rates of ACCase (Axial, Falcon, Stratos Ultra, Centurion Max) and ALS (Pacifica Plus or Monolith, Broadway Star) herbicides
The final results confirmed that 15 out of the 17 populations tested were resistant.
All 15 populations were ALS-resistant and 12 of those were also ACCase-resistant.