Weed Management

1
Weed Management
Joe Boggs Ohio State University Extension
2
Weed Management
Types of Weeds

• By Appearance
• Grassy Weeds (Crabgrass, Nimblewill)
• Broadleaf Weeds (Dandelion, Plantain)

• By Life Cycle
• Annual Weeds
• Biennial Weeds
• Perennial Weeds

3
Weed Management

• Types of Weeds
• By Life Cycle
• Annual Weeds
• Winter Annuals Henbit
• Summer Annuals Crabgrass, Prostrate Spurge
• Biennial Weeds Thistle
• Perennial Weeds Dandelion, Tall Fescue

4
Weed Management

• Management Strategies IPM

Integrated Pest Management
5
Weed Management

• Weed Control Strategies
• Cultural Control
• Clean Site (preventative, note topsoil).
• Cover Crops and Companion Plants
• Mulching
• Cultivation rototiller (note rhizomes,
  nutlets)
• Physical Removal hand-pulling
• Mowing

6
Weed Management

• Weed Control Strategies
• Chemical Control
• Herbicides are Classified three ways
• Mode of Action
• Range of Activity
• Targeted State of Weed Growth

7
Weed Management

• Herbicide Classification
• Mode of Action
• Contact Herbicides
• Systemic Herbicides
• Fumigants

weeds
weeds
weeds
weeds
8
Weed Management
Contact Herbicide

• kills on contact (surfactant often used)
• not absorbed and translocated
• very rapid activity (within hours)
• temperature dependent activity

• little or no soil activity
• usually used to control annuals, very poor
  control of perennials
• usually non-selective
• Examples Paraquat, potassium salts of fatty
  acids (soaps), pelargic acid (Scythe)

9
Weed Management
Systemic Herbicides

• absorbed by external tissues, translocated to
  sites of activity
• temperature dependent
• variable soil activity
• effective on both annuals and perennials

• both selective and non-selective forms
• Examples glyphosate (Roundup, a non-selective)
  clopyralid (Stinger, a selective for broadleaf
  weeds)

10
Weed Management
Fumigants

• kills wide range of organisms plants and plant
  parts (e.g. seeds), nematodes, pathogens,
  insects, etc.
• activity may be short or long duration -
  depending upon chemical, rate and environmental
  conditions (e.g. temperature).
• best activity in late summer/early fall high
  soil temps.
• Use seedbeds, potting soil, high-value
  landscape areas
• DANGEROUS inhalation
• Examples dazomet (Basamid Granular), methyl
  bromide, chloropicrin (Brom-O-Gas, Terr-O-Gas).

11
Weed Management

• Herbicide Classification Range of Activity
• Selective
• targets specific range of species
• examples halosulfron Manage (for nutsedge),
  fluazifop-p-butyl (Fusilade II), most
  preemergence.
• Non-Selective
• targets wide range of species
• examples glyphosate (Roundup),
  glufosinate-ammonium (Finale), potassium salts of
  fatty acids.

12
Weed Management

• Herbicide Classification Stage of Growth
• Preemergence Herbicide (Pre-emergent)
• Postemergence Herbicide (Post-emergent)

13
Weed Management

• Herbicide Classification Stage of Growth
• Preemergence Herbicide (Pre-emergent)
• inhibits seed germination
• usually selective
• variable length of activity
• most commonly use to control annual weeds
• examples Treflan (trifluralin), Surflan
  (oryzalin), Gallery (isoxaben).

14
Weed Management

• Herbicide Classification Stage of Growth
• Postemergence Herbicide (Post-emergent)
• kills plants once they have commenced vegetative
  growth
• both selective and non-selective types
• many involve synergistic response to max. control
• examples glyphosate (Roundup),
  glufosinate-ammonium (Finale), potassium salts of
  fatty acids.