Weed Control and Pesticides by ert554898

VIEWS: 3 PAGES: 22

									  Weed Control and Pesticides                 (chapter 10 p. 327-330, 338-350)


Control not eradicate
42% of total crop loss and cost.
   Crop yield: 10% - 17% yield loss =
     $80 - $136/A
   Crop quality: harvest, moisture,
                 unpalatable
   Disease and insects:
       rust, trips, curly top, grasshoppers
Yield losses greater in soybeans
  than corn.
Pesticides:
   Chemicals that kill or inhibit plant
      and/or animal life.
   Insecticides, fungicides, herbicides,
      rodenticides,
                       What is a Weed?
Weed = plant growing where not wanted               Corn
  Foxtails, velvetleaf, corn
True Weeds:
  1.   Seed production (75,000 – 500,000)
  2.   Rapid establishment
  3.   Seed dormancy
          7%-91% germination after 40 years
  4.   Long-term survival
  5.   Spread
Noxious Weeds:
  Prohibited: extremely difficult to control,
      unlawful to sell
  Restricted: hard to control, sale with limited
      amount
Common Weeds:
  No restrictions                         Canada
                                          Thistle
                 Weed Seed per Plant
Weed Species              # Seeds/Plant
Velvetleaf                     1,500
Yellow Nutsedge                 2,400
Giant Foxtail                  2,500
Pennsylvania Smartweed         3,000
Barnyardgrass                  7,000
Common Ragweed                15,000
Jimsonweed                    23,400
Shepard’s Purse               38,500
Curly Dock                    40,000
Common Purslane               52,000
Common Lambsquarter           72,000
Stinkgrass                    82,000
Redroot Pigweed              117,000
Black Nightshade             178,000
Russian Thistle              200,000
Witchweed                    500,000
                          Weed Biology
Grass, Sedge or Broadleaf (dicot)
   Grass weeds in grass crops difficult to
     control


Life Cycle:
   Annuals
   Biennials
   Perennials
   Weeds with similar life cycle to crop hard
     to control.
   Annuals easiest to kill not easier to control –
     why?

Herbicides Selectivity:
   Grass or broadleaf weeds             Yellow
   60% of all pesticides                Nutsedge
                     Weed Scouting
Field survey.
  50 acre sections.
  Map each section.
  Record management practices.
  Several weeks prior to field work.
     Continue throughout growing season.


Determine severity.

Determine treatment.
  Treatment effectiveness.
  Any crop damage.
               Noxious Weeds of Illinois

Common Ragweed (N)
Giant Ragweed (N)
Marijuana (I)
Musk Thistle (I)
                                     Kudzu
Canada Thistle (I)
Kudzu (I)
Perennial Sowthistle (I)
Columbus Grass (I)
Johnsongrass (I)
N = native, I = introduced
             Weeds of Field Crops

Weeds always present.
Excellent crop growth = excellent weed growth.
Common and difficult weeds of Illinois:
     Corn                 Soybeans
   Giant Foxtail          Giant Foxtail
   Fall Panicum           Wooly Cupgrass
   Waterhemp              Waterhemp
   Giant Ragweed (NW)     Giant Ragweed (NW)
   Velvetleaf             Velvetleaf
   Common Lambsquarters   Common Lambsquarters
   Common Cocklebur       Common Cocklebur
   Morningglory           Marestail
                        Pesticide Toxicity
Amount of pesticide
 harmful/lethal to humans.

Acute or chronic
Oral, dermal or inhalation         SevinTM = 800 mg/kg = 28 grams
   Rate of pesticide absorption:   TemikTM = 0.79 mg/kg = 0.04 grams
           Scalp = 3.7
           Forehead = 4.2
           Ear Canal = 5.4
           Forearm = 2.1
           Abdomen = 2.1
           Palm = 1.3
           Testicles = 11.8
           Ball of Foot = 1.6
                LD50 of Common Chemicals
Sucrose (table sugar)         29,700             Caffeine Amounts (mg)
Trifluralin (Treflan)          5,000                   Double Espresso = 160
Glyphosate (Roundup)           5,000                   Drip Coffee     = 90
Baking soda                    4,200                   Cola           = 45
Table salt                     3,800                   Chocolate Bar   = 25
Atrazine                       3,100                   Green Tea      = 15
                                                       Decaffeinated  = 5
Ethanol                        2,080
Aspirin                        1,800
Alachlor                       1,200             Or, a person weighing 200 pounds:
                                                       194 cups of coffee
Sevin                            800                    42 cups of coffee in several
2,4-D                            800                        hours
Paraquat                         200                   388 cans of soda
Caffeine                        192                    Salt shaker contents all at once
Sarin                             24                   100 8 oz. glasses of water in 2
                                                            hours
Sodium Cyanide                     6.4
Temik                                .79
VX                                   .14


LD50 (Lethal Dose, 50%)= mg/kg human body weight to kill 50% of the individuals tested.
                Toxicity of Herbicides

Danger – Poison:
   Gramoxone Max or Cyclone Max = paraquat
Danger – Corrosive:
   Assure, Cobra, Laddock S-12, Shotgun, Storm,
Warning:
   Banvel, Buctril, Harness, Liberty, Lightning, Poast, Pursuit
Toxic to Fish:
   Buctril, Prowl, Pursuit Plus, Fusilade, Fusion, Horizon
                        Pesticide Label
Legal document and subject to severe penalty.
1.   Name and Address of Manufacturer:
2.   Name of Product: Roundup
3.   What Product is: selective or contact
4.   Active Ingredient: active chemical
     Glyphosate – Roundup(s), Touchdown, Cornerstone
     Imazapyr – Arsenal, Stalker
     2-4-D – many
5.   Percent Inert Ingredients: aids dispersal
6.   EPA Registration Number: proof EPA approved
7.   Establishment Number: identifies facility
8.   Classification Statement:
     General – do not harm user or environment unreasonably.
     Restricted - may harm user or environment
                  application by certified operator
9. Directions for Use: rate, crops, pests, timing, etc.
10. Mode of Action: method of killing pest
                               Pesticide Label
11.    Signal Words: level of toxicity
12.    Toxicity: LD50
          Danger – teaspoon or less kills
          Warning – teaspoon to 1 oz. kills
          Caution – greater amounts harmful
13.    Precautionary Statements:
          Worker Protection Standards (WPS):
          Personal Protective Equipment (PPE):
          Restricted Entry Intervals (REI):
14.   Statement of Practical Treatment: first aid
15.   Environmental Hazard Statement:
16.   Reentry Statement: reenter field
17.   Formulation:
          Liquid, wettable powders, emulsifiable
          concentrate, soluble powder
18. Handling, Storage, Disposal:
                       Herbicide Selectivity
Classification:
   Selective: kills certain weeds (2-4-D)
   Nonselective: kills any plant (Roundup)
                   Tank mixes: Mecocap + Dicamba +2-4-D
   Soil Sterilants: kills all, Methylene Bromide
   Atrazine:
       Low Rate = selective
       High rate = nonselective
       Very High Rate = soil Sterilant
Application:
   Broadcast: uniform across field
   Banded: bands over rows
   Spot: weed problem areas
   Directed: bases of stem
                Site of Herbicide Action
Translocated Herbicides:
   Taken up by roots.
   Most herbicides.
   Pre-plant incorporate and post-
     emergence.
   Important for perennial weed control.
   2-4-D, Accent, Beacon, Basis, Roundup,
     Banvel
Contact Herbicides:
   Kills on contact
   Requires surfactant or wetting agent
   Most are nonselective.
   Atrazine, Basagran, Liberty, Laddock,
      Buctril, Paraquat
                           Mode of Action
Method of killing weeds.
• Inhibit lipid or amino acid synthesis:
    Roundup – absorbed by plant,
             translocated to growing points.
       Inhibits amino acid synthesis.
• Chlorophyll formation:
      Pigment inhibitor
• Photosynthesis:
• Growth regulators:
    Interfere with metabolism
    2-4-D: ALS (acetolactate synthesis)
       inhibitor
• Disrupt cell membranes:
                     Time of Application
Preplant:
   10-30 days before seeding
Pre-emergent (PRE):
   Before emergence.
      Advantage: banded with planter
      Disadvantage: limited herbicide choice
Postemergent (POST):
   Applied after crop emerged.
      Previous application failed.
   Mid-day application best. Why?
            Length of Herbicide Activity
Essential for first 4-6 weeks
No carryover
Non-residual:
  Post-emergent.
  Toxic for short period.
  Broken down by sun or microorganisms.
  Attached to soil particles.
  Leach or evaporate.
Residual:
  Toxic for weeks to >one year (Atrazine).
  Affected by: rain, pH, temperature, organic matter, soil
    texture
                   Pesticide Resistance
1950’s: 2-4-D resistant dandelion and wild carrot
1968: triazine resistant groundsel
Currently: 180 resistant weeds
   RoundupTM resistant marestail, rigid ryegrass, waterhemp, goosegrass
     and daisey fleabane, morningglory,wild buckwheat, Pennsylvania
     smartweed, lady’s thumb, Venice mallow, yellow sweetclover, field
     bindweed, kochia, Russian thistle, primrose, so far.

Types:
   Resistance = plant of susceptible species no longer
                susceptible
   Tolerance = species has never been susceptible
   Cross-Resistance = same mode of action in several herbicides
   Multiple-Resistance = resistance to several herbicide classes
                      Origin of Resistance
                                                    Wild Oat Herbicide Resistance
Mutation Theory:
   Genetic mutation in plant after herbicide
        applied.
   ATTCGCGTA  ATTCCCGTA
   Not widely accepted.
Natural Selection Theory:
   Resistant plants always existed in low number.
   Resistant plants survive and reproduce.
   Key Factors:
   1.   Single site of action.
   2.   Repeated use.
   3.   No other control measures.
              Basis for Weed Resistance
Alteration of Target Site:
   Most common occurrence.
   Single site  single gene
   Triazines, ALS, and ACCase
Enhanced metabolism of
  Herbicide:
   Plant detoxifies herbicide by
      metabolism.
                                           RoundupTM - Ryegrass in Australia
   Inactivates herbicide before it reaches
      active site.
   Atrizine resistant velvetleaf.
   RoundupTM resistance

                   ALS Resistant Foxtail
                   Raptor/Accent/Pursuit
                 Management Strategies
1.   Scout fields.
2.   Rotate herbicides.
3.   Use tank mixes, prepackaged or sequential mixtures.
4.   No more than 2 consecutive applications of herbicides with
     same site of action.
5.   Combine mechanical and chemical control.
6.   Clean tillage and harvest equipment between fields.
       Resistant weed usually confined to field for 1-2 years.
       Control isolated weed patch with other herbicides.
           Diagnose Herbicide Resistance
1.   All other causes of failure eliminated.
2.   Other weeds on label controlled.
3.   Field history of continuous use of site of action.
4.   Weed controlled in past.

								
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