Worrying picture painted on herbicide resistance
The results of herbicide resistance testing from 2023 harvest samples paint a worrying picture.
Greater than 75% of blackgrass or Italian ryegrass tested was resistant to ACCase (Axial, Falcon, Stratos) and/or ALS (Pacifica, Broadway) herbicides. We also found chickweed, corn marigold and speedwell resistant to ALS-type (Ally Max) herbicides, and poppy resistant or tolerant to ALS and/or hormone type (2,4-D, Zypar) herbicides.
Teagasc has initiated a Weed Watch campaign with the Irish Farmers Journal to encourage growers and industry to test their resistance suspect grass or broadleaved weeds (specifically blackgrass, Italian ryegrass, poppy or speedwell).
The programme uses Oak Park’s unique free testing service to identify an effective herbicide programme to be used in conjunction with integrated approaches. Good sample collection is essential for successful testing. Contact your advisor, or follow the instructions on the application form (PDF) available here.
Glyphosate label changes
As a result of the re-registration of the glyphosate products, there are some significant changes to the labels (including changes in PCS numbers), which will impact on the use of glyphosate.
Summary of main changes (rates based on 360g/L product):
- Harvest management on oilseed rape is not allowed – now weed control only, same as cereals;
- Pre-harvest use on beans is not allowed in any circumstance;
- Pre-harvest weed control is only allowed when the crop is greater than BBCH 87 and grain/seed moisture is less than 30%;
- Grassland destruction maximum rate is now 4L/ha - it was 6L/ha;
- For post-planting and pre-crop emergence, the maximum rate is now 1.33L;
- The maximum rate for non-crop areas is now 5L/ha - it was 6L/ha.
Authorisations for the ‘old’ label products expired on March 31, 2024. However, existing stocks of these products can be used up until September 30, 2025.
This article first appeared in the July Teagasc Tillage Advisory Newsletter, edited by Teagasc Tillage Specialist, Ciaran Collins. Access the full publication here.
Also read: Weed Watch 2024: Herbicide resistance testing
Also read: Grass weeds - a growing problem on Irish tillage farms