Germinal provides an overview to help farmers control weeds in their grassland by applying herbicide sprays effectively.
Weed control in new leys
- Postemergence spray of new ley is the most cost-effective spray you will use
- Control of docks, thistles, chickweed etc is much more effective at the seedling stage
- Product choice is dependent on if clover is present in the new ley or not
Which weeds do I need to worry about?
Annual weeds such as Fumitory, Fat Hen, and Deadnettle only live for 1 year. These weeds should not affect the establishment of the new sward (unless present in high numbers – if so spray them). They are normally removed by grazing, cutting or leaving them to die naturally over winter.
Perennial Weeds such as Docks, Dandelions, Creeping Buttercup and Creeping Thistle can be tolerated (at low numbers) in an intensive grazing situation. However, it is still better to spray them now rather than in a few years time. In silage/hay fields, you should always spray for these perennial weeds after reseeding as they will build up their root reserves and take over the grass.
Help the spray work
- Have an even, vigorously growing sward.
- Apply the herbicide onto small, actively growing weeds (e.g. dock leaf = size of €2 coin)
- Spray 6-8 weeks after re-seeding when there are 3 leaves on the grass and 1 true leaf on the clover
- Avoid spraying in very dry or cold conditions (talk to your advisor/merchant if this is the case).
- Keep water rates high – as per label recommendations
- Remember to keep the prescribed cross-compliance records and follow the product label
Weed control in established grassland
- Always check the label for usage rate and water volume before use
- Avoid spraying when waterlogged, drought stress or cold stress
- Ensure weeds are growing actively with healthy leaves for successful control
- Consider watercourses, weather, weed health before spaying
- Cutting/ grazing restrictions may need to be extended to allow for poisonous weeds. E.g. ragwort
- Follow the product label for application rate and water rate. Keep prescribed cross-compliance records
- Use the appropriate spay for the weeds you are targeting
- Most sprays e.g. Dockstar, Forefront, Eagle, Thislex are okay to graze 7 days post-application, but 3-4 weeks if cutting silage
Herbicides for weed control in new leys (last updated 2016)
| Trade Name | Clover Safe | Rate/ha | Comment | Notes |
Legumex DB Undersown Clovex DB Plus | Yes | 7 l/ha | Controls moderate levels of docks, thistles, etc and most annual weeds. Needs small actively growing weeds for best effect. Apply after 2 leaf stage of grass and from 1 leaf clover stage. | MCPA + 2,4, DB |
Legumex DB + Triad | Yes | 5.0 L/ha + 10 g/ha | Best broad spectrum clover-safe option Apply after 2 leaf stage of grass and from 1 leaf clover stage. Add Triad to the tank first and then Legumex DB. | MCPA + 2,4, DB Addition of Triad is necessary for control of chickweed |
| Underclear | Yes | 7 L/ha | Good control at seedling stage (cotyledon to 2 or 3 leaves) and possibly a useful suppression at later growth stages: Docks (seedling) Field Bindweed, Plantain spp, Field horsetails, Sorrel spp, Perennial Sow Thistle, Spear Thistle. | 2,4-DB + Mecoprop-P |
| Starane2, Binder, Hurler, Reaper | No | 0.75 L/ha | Best option for high numbers of docks, chickweed, dandelion, nettles. Limited use on thistles and buttercups. Apply from 3 leaf grass stage | Active ingredient Fluroxypyr |
| PastorTrio | No | 1 l/ha | Chickweed, fat-hen, mayweeds, buttercups, docks and thistles | Active Ingredient fluroxypyr + clopyralid + florasulam. Permitted 1st Feb to 31st August in new sown leys |
(Source: Teagasc 2016)
Cutting/ grazing restrictions may need to be extended to allow for poisonous weeds. E.g. ragwort
Follow the product label for application rate and water rate. Keep prescribed cross-compliance records.
Herbicides for dock control in established grassland
| Problem | Solution | Rate | Grazing Interval | Clover Safe | Water Volume | Notes |
| Docks & Chickweed | Dockstar | 3.0 l/ha or 1.5 +1.5 l/ha | 7 days | No | 300-400 l/ha | Do not cut silage for 4 weeks after application |
| Docks, thistles, nettles, buttercups, dandelions, ragworth | Forefront T | 2.0 l/ha | 7 days | No | 200 -300 l/ha | Use on grazing ground only |
| Thistles | Thistlex | 1.0 l/ha | 7 days | No | 200-400 l/ha | Do not cut silage for 3 weeks after application |
| Docks | Eagle | 40-60 g/ha | 7 days | Yes | 200-400 l/ha | Do not cut silage for 3 weeks after application |
- Always check the label for usage rate and water volume before use
- Avoid spraying when waterlogged, drought stress or cold stress
- Ensure weeds are growing actively with healthy leaves for successful control
- None of the above is approved for use in hand-held equipment
- Consider watercourses, weather, weed health before spaying
Feel free to explore our Knowledge Hub for even more helpful grassland management advice.