VIEWS: 3 PAGES: 22 POSTED ON: 5/6/2012
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.
Pages to are hidden for
"Weed Control and Pesticides"Please download to view full document