Weed Identification and control

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Weed Identification and control
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Weed identification and control

• I. History of weed control large scale
  agriculture to the home gardener
• II. Weed identification
• A. Grasses
• B. Broadleaves
• III. Weed control
• A. Herbicides
• B. Other options
• IV. Specific examples and questions

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World population
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Pesticide regulation

• Clinton
• -Must reduce pesticide use by 50 by the year
  2002.
• -Must have 75 of American farmland managed with
  IPM strategies.

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The search for alternatives

• Herbicides constitute 70 of all pesticide use.
• With current pesticides, we still lose 40 of our
  crops to pests.
• Result must find alternative and integrated weed
  control strategies.

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Weed identification
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Weed control
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Weeds

• Since the best way of weeding
• Is to prevent weeds from seeding,
• The least procrastination
• Of any operation
• To prevent the semination
• Of noxious vegetation
• Is a source of tribulation.
• And this, in truth, a fact is
• Which gardeners ought to practice,
• And tillers should remember,
• From April to December.
• -New England Farmer, 1829

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Why control weeds?

• Weeds harbor diseases and insects
• Take moisture, nutrients, and light from the crop
• Reduce quality, crop yield and interfere with
  harvest
• Aesthetics and allergies
• Weeds always win!

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Why weeds always win

• Prolific seeders
• Dormancy - wait until conditions are favorable
• Seed dispersal
• Genetic diversity
• Long-term seed viability

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Keys to good weed control

• Know your weeds!
• Timing is critical
• Short term minimize weed-crop competition
• Long-term prevent weed seed production

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Chemical control pros and cons

• Pros
• Residual control with preemergent herbicides
• Decreased labor input (limited hoeing!)
• Less soil disturbance reduced weed germinations
• Cons
• Environmental and human toxicity
• Expensive - specialized equipment required
• Potential for drift and carryover

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Roundup

• Non-selective
• Contact herbicide - works only postemergence
• Translocates through the plant - control symptoms
  may not appear for 2-3 weeks
• Inhibits amino acid synthesis
• Symptoms include foliar chlorosis, leaf wilting,
  leaf malformation, and necrosis

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Roundup

• Species controlled
• All annual weeds
• Some established perennials may require repeat
  applications
• Species safe
• None!

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Treflan

• Selective herbicide kills some species while not
  injuring others.
• Preemergence, incorporated
• Requires moisture to activate herbicide
• Inhibits root growth by preventing cell wall
  formation
• Symptoms include enlarged roots, clubbed roots,
  and poor seedling vigor.

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Treflan

• Species controlled
• foxtails, barnyardgrass, purslane, lambsquarters,
  chickweed, pigweed, and field bindweed
• Labeled for multiple vegetable crops
• see label for use

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2,4-D

• Selectively controls broadleaves
• Postemergence
• Drift!
• Translocates from source to sink
• Action similar to natural hormone IAA
• Symptoms include epinasty thickening and
  curvature of stems and petiole

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2,4-D

• Species controlled lambsquarter, pigweeds,
  ragweed, velvetleaf, and canada thistle
• Labeled on multiple vegetable crops
• see label for use

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Poast

• Selectively controls grasses
• Postemergence
• Drift!
• Loss of fatty acid synthesis decreases production
  of chloroplasts
• Grass growth ceases soon after application
• Symptoms include loss of vigor, pigment changes,
  and necrosis ( 1-3 weeks )

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Poast

• Species controlled barnyardgrass, quackgrass,
  and foxtails
• Labeled on multiple vegetable crops
• see label for use

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Alternatives

• Hoeing and handweeding
• Stale seedbed
• Flaming
• Interseeding
• Living and dead mulches

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Mulches

• A 3-4 layer will smother many weeds
• Dead mulches compost, leaves, sawdust, grass
  clippings, straw, wood chips, plastic, newspaper,
  etc.
• Living mulches clovers, vetches, ryegrass,
  alfalfa, buckwheat, oat.

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Mulches pros vs. cons

• Pros
• 1. Prevent weed germination
• 2. Keeps soil moist and cool
• 3. Decomposition releases nutrients
• Cons
• 1. Harbors disease, insects, rodents, and slugs
• 2. Keeps soil moist and cool
• 3. Many mulches are acidic

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IPM and home gardener

• Know your garden
• Scout for weeds, insects, and diseases
• Maintain detailed journal of garden
• past problems
• varieties
• locations
• activities
• Rotation in garden
• Have Fun!!