Weed control in grassland

Weed control in new leys

  • Post emergence spray of new ley is most cost effective spray you will use.
  • Control of docks, thistles, chickweed etc is much more effective at seedling stage
  • Product choice is dependent on if clover is present in the new ley or not.

What 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 die naturally over winter.

Perennial Weeds such as Docks, Dandelions, Creeping Buttercup, and Creeping Thistle etc can be tolerated (at low numbers) in an intensive grazing situation, however it is still better to spray them now rather then in a few years time. In silage/hay fields you should always spray for these perennial weeds after re-seeding 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 water courses, weather, weed health before spaying
  • Cutting/ grazing restrictions may need to be extended to allow for poisonous weeds. E.g. ragwort
  • Follow the product lablel for application rate and water rate. Keep prescribed cross compliance records.
  • Use 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 SafeRate/haCommentNotes

Legumex DB

Undersown

Clovex

DB Plus

Yes7 l/haControls 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

UnderclearYes7 L/haGood 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, ReaperNo0.75 L/haBest option for high numbers of docks, chickweed, dandelion, nettles. Limited use on thistles and buttercups. Apply from 3 leaf grass stageActive ingredient Fluroxypyr
PastorTrioNo1 l/haChickweed, 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 lablel for application rate and water rate. Keep prescribed cross compliance records.

Herbicides for dock control in established grassland

ProblemSolutionRateGrazing Interval Clover SafeWater VolumeNotes
Docks & ChickweedDockstar3.0 l/ha or 1.5 +1.5 l/ha7 daysNo300-400 l/haDo not cut silage for 4 weeks after application
Docks, thistles, nettles, buttercups, dandelions, ragworthForefront T2.0 l/ha7 daysNo200 -300 l/haUse on grazing ground only
ThistlesThistlex1.0 l/ha7 daysNo200-400 l/haDo not cut silage for 3 weeks after application
DocksEagle40-60 g/ha7 daysYes200-400 l/haDo 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 are approved for use in hand-held equipment
  • Consider water courses, weather, weed health before spaying

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