Herbicide Recommendations for Pastures (Mostly grasses): Postemergence Biennial and Perennial Weed Herbicides

Excerpt from 2008 Publication 75, Guide to Weed Control, Order this publication

Table of Contents

1. Introduction
2. 2,4-D
3. 2,4-D + Banvel II
4. Caliber 400, Cobutox 600 or Embutox 625
5. Amitrol 240
6. Banvel II
7. Glyphosate (for colt's-foot)
8. Glyphosate (for tansy)
9. Glyphosate (for Canada thistle, field bindweed and milkweed)
10. MCPA
11. Milestone
12. Milestone + 2,4-D Amine
13. Clovitox Plus, Topside or Tropotox Plus
14. Forage Crops Herbicide Weed Control Ratings (Table 10-1) (PDF file - 62 kb)
    • Annual Grasses
    • Broadleaf Weeds
    • Perennial Weeds
15. Other Forage Crops Weed Control Recommendations
    • Forage Legumes
    • Forage Sorghum and Forage Millet
    • Pasture Renovation with Bird's-foot Trefoil
16. Stages of Leaf Development
    • Alfalfa, Red Clover Ladino, Aslike and Black Medic
    • Bird's-foot Trefoil
17. Related Links

Introduction

Biennials: Unless otherwise noted, most chemicals are best applied in early fall to first year growth or in late spring to second year growth.

Perennials: Unless otherwise noted, apply in late spring (end of May to mid-June) when weeds are actively growing. Overgrazing tends to thin the grass stand and allows the establishment of weeds. Undergrazing allows weeds like wild carrot to form and spread seed. Timely mowing can prevent the ripening of weed seeds and reduce the distance these seeds spread with the wind.

• Chemicals are available to control most of the troublesome weeds in grass pastures and these can give faster kill of established weeds than any other management practice. A chemical may have to be applied more than once to kill established perennial weeds and the new crop of weeds that emerges through a thin grass stand. A poor grass stand can be improved by using a combination of chemicals, fertility and grazing management.
• Extend chemical weed control into fencerows and other areas around the pasture to keep these areas from becoming sources of weed seeds.
• Generally, clovers are severely damaged by chemical treatments. However, white clover and black medic show some resistance and re-establish quickly.
• Consult the label to determine the period of time to keep livestock out of the treated area.
• Prevent grazing where poisonous plants (water hemlock, buttercup, chokecherry, etc.) may be made more attractive to livestock after the chemical treatment. It is a good practice to prevent grazing on the field for at least a week after spraying to reduce the chances of the livestock consuming harmful plants.
• Apply chemical treatments in at least 200 L/ha (80 L/ac) water and increase this rate if it is necessary to contact weeds through dense vegetation.
• Avoid drift or vapour drift from 2,4-D or dicamba onto susceptible crops by using drift reducing techniques such as high spray volume, coarse droplets or anti-drift nozzles.

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Precautions

• Use the low rate for chicory.
• Use the high rate for:
• Goldenrod.
  
• Yellow rocket: Mow before spraying if plants are in flowering stage.
• Blueweed and burdock: Apply as low volatile ester.
• Wild carrot: Early spring or early fall. If 2,4-D resistant strains are present, mow to reduce seed spread.
• Goat's-beard: Early spring or early fall.
• Milkweed: Spray undersides of leaves. Only top growth is killed.
• Water hemlock: Apply in May or June.
• Dandelion: Can also apply in September
• Ox-eye daisy and hawk's-beard: Use 2 treatments, one in late spring and the second in early September if there is sufficient growth.
• Tansy ragwort: Apply to rosettes in spring or fall; Retreat as necessary to control new seedlings and regrowth.

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Precautions

• For wild carrot. Apply in early fall for control of first year plants.
• Wait 14 days between treatment and harvest or grazing for dairy animals.
• Meat animals may graze or feed in treated pastures 30 days after dicamba application without restrictions on slaughter.
• If treated vegetation has been consumed by meat animals within 30 days of dicamba application, feed the animals with untreated diet for 30 days before slaughter.

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Precautions

• Nodding, Scotch, or bull thistles, perennial sow thistle, and chicory: Apply to rosette stage.
• Yellow rocket: Apply in fall.
• Plantains: Apply before flowering.
• Curled dock: Apply to early growth.
• Top growth only controlled for:
• Canada thistle: Apply when 15 cm high to early bud stage.
• Field bindweed: Apply in late summer.
• Dandelion: Apply before bud stage.
• Horsetail: Apply at 10-12 cm tall
• Do NOT graze or cut for forage in the year of treatment.

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Precautions

• SPOT TREATMENT ONLY
• Lower rate for dandelion, Canada thistle, sow-thistle, hoary cress, milkweed, poison-ivy, and toadflax.
• Higher rate for horsetail and leafy spurge.
• Use spot treatments.
• Spray to wet before flowering.
• Keep animals away from treated area for 6-8 months.

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Precautions

• For all rates: Meat animals may graze or feed treated pastures 30 days after dicamba application without restriction to slaughter. If treated vegetation has been consumed by meat animals with animals 30 days of dicamba application, feed the animals with untreated diet for 30 days before slaughter.
• Leafy and cypress spurges: For control of top growth, apply when weed is actively growing; No delay required between treatment and harvest or grazing for dairy animals.
• Tansy ragwort: Apply when weed is actively growing; Wait 7 days between treatment and harvest or grazing for dairy animals.
• Goldenrod: Apply when weed is actively growing; Wait 14 days between treatment and harvest or grazing for dairy animals.
• Canada thistle and field bindweed: Apply at the bud stage of thistle and at the flowering of bindweed; Wait 14 days between treatment and harvest or grazing for dairy animals.
• Goat's-beard: Apply when weed is actively growing; Wait 14 days between treatment and harvest or grazing for dairy animals.

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Precautions

• SPOT TREATMENT ONLY
• For colt's-foot: apply when leaves are fully expanded.
• Wait until the treated areas have turned brown before grazing.

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Precautions

• SPOT TREATMENT ONLY
• For tansy: apply when tansy is in bud to full bloom stage.

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Precautions

• SPOT TREATMENT ONLY
• For Canada thistle, field bindweed and milkweed.
• Always use high rate for milkweed.
• Apply when thistle and milkweed are in the bud to full bloom stage and bindweed is flowering.
• Wait until the treated areas have turned brown before grazing.

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Precautions

• For buttercup: use 2 treatments, one in June and the second in early September.
• Wait 7 days after treatment before grazing.

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Precautions

• Apply Postemergence.
• Will control: Absinth (Biennial) Wormwood, Goldenrod, Knapweed, Scentless Chamomile, Canada Thistle, Yellow Star Thistle, Musk (nodding) Thistle, Sulphur Cinquefoil and Tropical Soda Apple
• Will suppress: Common tansy and Dandelion
  

• Apply Postemergence.
• For wider spectrum of weed control, 2,4-D amine may be added at a ratio of 1 part Milestone ai/ha to 12 parts 2,4-D amine ai/ha.