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Weed Control


Weed Control Topic 2044 Melissa M. Fowler What is a Weed? Any plant that is out of place Any plant that grows where it isn t wanted Examples A corn plant growing in ... – PowerPoint PPT presentation

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Title: Weed Control

Weed Control
  • Topic 2044
  • Melissa M. Fowler

What is a Weed?
  • Any plant that is out of place
  • Any plant that grows where it isnt wanted
  • Examples
  • A corn plant growing in a soybean field
  • A tulip growing in the middle of a yard

Detrimental Effects
  • Compete with crops for
  • Moisture
  • Light
  • Nutrients
  • Contaminate crops and their products
  • Off flavored milk
  • Weed seeds in a seed crop
  • Carry pathogens

Detrimental Effects Cont.
  • Poisonous to livestock
  • Loco Weed
  • Nightshade
  • Milkweed
  • Increased production costs
  • Cultivation
  • Chemicals
  • Seedbed preparation
  • Nuisance

Beneficial Effects
  • Prevent erosion
  • Provide food and cover for wildlife
  • Reduce leaching of minerals
  • Add organic matter

Eradication vs. Control
  • Eradication
  • Killing every existing plant
  • Destroying all reproductive organs
  • Dormant seeds
  • Below ground organs
  • Control
  • Reducing existing plants
  • Presence of some weeds does not seriously
    interfere with the areas economic use.

  • Use clean, weed-free seed
  • Use clean equipment
  • Grow weed-adapted crops
  • Watch for weed seeds in packing material or
    nursery stock

Methods of Control
  • Biological
  • Mechanical
  • Chemical

Biological Control
  • Caterpillars
  • Used to kill thorny shrubs
  • Fungus
  • Velvetleaf will wilt and die
  • No harm to crops or ornamentals
  • Fungal Spores
  • Sprayed on rice crop
  • Weeds controlled within 7 to 10 days
  • As effective as herbicides
  • No damage to rice

Biological Control Cont.
  • Allelopathy
  • Plants produce chemicals
  • Chemicals harmful to other plants
  • Chemicals exude through plant roots or will be
    washed from leaves by rain

Mechanical Control
  • Cultivation
  • Uproot and/or cut off roots
  • Mulches
  • Layer of plant or artificial material on soil
  • Work by cutting off light source
  • Burning (1800oF)
  • Flame directed on weeds for short time
  • Done in cotton
  • Effective for killing small weeds

Mechanical Control Cont.
  • Flooding
  • Used on rice paddies
  • Kills non-aquatic weeds

Chemical Control
  • Herbicides
  • Depend on rain to wash them into soils
  • Types of Application
  • Preplant
  • Preplant incorporated
  • Preemergence
  • Postemergence

Herbicide Types
  • Contact
  • Kills the part of the plant that it touches
  • Not carried throughout the plant
  • Will not kill perennial weeds
  • Example Paraquat
  • Systematic
  • Blocks metabolic activity
  • Translocated throughout the plant
  • Necessary to kill perennial weeds
  • Example Roundup

Herbicide Types Cont.
  • Selective
  • Kills one type of plant but not another
  • Some will kill broadleaves, but not grasses
  • Others will kill some grasses and some
    broadleaves, but not others
  • Example Atrazine
  • All selective herbicides are systematic BUT not
    all systematic herbicides are selective.

  • Sticking agent added to help herbicides stick
  • Facilitate absorption of chemical
  • Also known as Crop Oil Concentrate (COC)

Active Ingredient (a.i.)
  • Ingredient that actually kills the plant
  • Pounds/ acre
  • Ounces/ acre
  • Too little will not work sufficiently
  • Too much will harm the crop and cause pollution
  • Follow label directions
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