Pasture Weed Management

1
Recognizing and Managing Pastures Weeds Lecture
21 B
2
Good Management Gives 90of Your Pasture Weed
Control
_________
Controlled grazing - clipping
Preventative measures
Dense stand Proper fertility
3
Common Weeds in Pastures

• Annuals
• Ragweeds
• Smartweeds
• Yellow foxtail
• Biennials
• Bull thistle
• Plumeless thistle
• Musk thistle
• Burdock
• Wild parsnip

• Perennials
• Canada thistle
• Goldenrod
• Curly dock
• Horsenettle
• Chicory
• Brush
• Willows
• Box elder
• Multiflora rose
• Prickly ash

4
Thistle Identification
5
Thistle Biology

• They vary in life cycle
• Annuals ___________________
• Biennials bull, musk and plumeless
• Perennials Canada and perennial sowthistle

6
Bull Thistle

• leaves deeply cut, witha wrinkled,
  gray-greensurface
• Midvein of leaves
• often whitishspines needle-like

7
Bull Thistle

• stem appears spiny
• decurrent leaves(run down along stem)

8
Bull Thistle

• inflorescence flask-shaped

9
Musk Thistle

• leaves smooth, withgray-green margin andwhite,
  hairless midrib
• No hairs on either side of the leaf

10
Musk Thistle

• stem spiny exceptbelow flower head
• inflorescence1.5 to 2" across

11
Plumeless Thistle

• leaves deeply divided
• leaves hairy esp. lowersurface midrib
• leaf lobes often at anangle to midrib

12
Plumeless Thistle

• stems spiny from base to tip
• inflorescence .75 to 1.5" wide

13
Canada Thistle

• leaves spiny withcrinkled, spiny edges
• roots deep and branched

14
Canada Thistle

• flowers pink-purple flaskshaped, 3/4 inch wide
• grows in patches male and femaleflowers on
  separate heads plants

15
Spotted Knapweed

• Another biennial (or short-lived perennial)
• Loves sandy soil
• Prolific seed producer
• Inhibits growth of other plants

16
Spotted Knapweed

• Leaves and stemsare coarse and rough textured
• Flowerheads pretty
• Bracts are blackenedon tips thus the
  namespotted knapweed

17
Burdock ________________
18
Biennial Weed Management

• Key to long-term
• control is
• ________________

19
When to Treat Biennials?

• Best results when treated in seedling or rosette
  stages
• this is any time in the year of germination
• and up to bolting stage in second year
• After bolting, ___________is best option
• They can also be controlled by cutting just below
  the soil surface.

20
When to Treat Biennials?

• ___________ applications ideal
• all plants of concern in rosette stage
• active translocation to crown/roots
• less hectic time of year

21
What to Use for Biennials?

• Growth regulator herbicides all effective
• 2,4-D, dicamba (Clarity/Banvel), Stinger and
  others
• Several premixes available
• WeedMaster 2,4-D dicamba
• Crossbow 2,4-D Garlon
• Glyphosate (Roundup and company) may fit in some
  situations

22
Glyphosate in Spot Applications

• Use with caution Glyphosate _____________________
  _____________
• Appropriate for small infestations
• Use backpack sprayer with single nozzle
• No need to treat entire plant aim for the
  rosette center

23
Glyphosate in Selective Applicators

• Effective on weeds taller than forages
• Safe to shorter grasses and legumes
• May not kill thistles but usually prevents seed
  production

24
When to Treat Canada Thistle(and other
herbaceous perennials)

• Best timing is in ______________________stage
• Stinger Effective on Canada thistle but
  expensive
• Dicamba (Clarity/Banvel) alone or with 2,4-D
  more economical but less effective long-term

25
Yellow Foxtail
Flattened stem
26
Yellow Foxtail
27
Yellow Foxtail Biology

• An annual grass that spreads/increases annually
• A true opportunistic weed
• Why so common in some pastures?
• Over grazing?
• Poor pasture stands/mixes
• Heavy grazing followed by rain event?
• Hot, wet periods?
• Low nitrogen levels?

28
Yellow Foxtail Control in Pasture

• Prevention the best medicine
• Clipping helps but impossible to prevent all seed
  production
• Plateau now labeled for pastures
• Claims yellow foxtail control at 4 oz/a
• Timing important and challenging

29
For All Treatments in Pastures

• Take inventory on weed regrowth or species
  changes
• the season applied
• and several times annually thereafter

30
Get it All Together
Chemical
Mechanical
INTEGRATED (Diversified)
Cultural