the pesticide dilemma

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Chapter 23. The Pesticide Dilemma. Perfect Pesticide. Easily biodegrade into safe elements Narrow Spectrum - kill target species only Remain put in applied location in environment. Prior to the 1940 s. 1st generation Inorganic - lead, mercury, arsenic Persistent and stable - PowerPoint PPT Presentation


  • The Pesticide Dilemma Chapter 23

  • Perfect PesticideEasily biodegrade into safe elements

    Narrow Spectrum - kill target species only

    Remain put in applied location in environment

  • Prior to the 1940s1st generation

    Inorganic - lead, mercury, arsenicPersistent and stableToxic to animals2. Organic (botanicals) - nicotine, pyrethrin, rotenoneEasily biodegradeDo not persistToxic to bees and fish

    3. Synthetic Botanicals = second generation

  • Second-Generation PesticidesSynthetic botanicals (DDT) - persistent & stable

  • Benefit - Disease Control

  • Malaria Snapshot247 million cases of malaria in 2006, causing about 880,000 deaths, mostly among African children.

    Approximately half of the world's population is at risk of malaria most low income countries

    Economic toll

    Insecticide-treated nets

    Increasing mosquito resistance to insecticides

  • The Major Pesticide GroupsChlorinated hydrocarbon (DDT) Broad-Spectrum persistent nonpolar

    OrganophosphatesBroad-spectrum: very toxic to mammals, birds, fishNerve agentDegrades rapidlyMore toxic than Chlorinated Hydrocarbons

    Carbamates Broad-spectrum similar function to organophosphates but reversible and less toxic to mammals - degrades rapidly

  • Bioaccumulation

    Synthetic substances typically not metabolized - accumulate in fat

    Fat soluble (lipophilic) substances cannot be excreted in urine, a water-based medium, and so accumulate in fatty tissues.

  • Pull on a star and you find the universe attachedProblems: Mobility PersistenceBioaccumulationBiological Magnification

  • Biomagnification

  • BiomagnificationExample: Effect of DDT on bald eagles

  • Major HerbicidesSelective herbicides - (2,4,5-T & 2,4-D kills broad-leaved plants)Nonselective herbicides(glyphosate, aka: Round-UpTM)

  • Alternatives - GMOsBacillus thuringiensis (Bt) Corn & Cotton (roundup ready)non-target species monarch butterflySoil accumulation of Bt1. Growers plant 80% corn acres with Bt corn - 20% planted with non-Bt corn (refuge area).2. Refuge area must be within 1/2 mile of Bt field.

  • Lawn Care

  • Benefits - Initial ReturnsCrop productionSavings of 3-5$ in crops for every $1 invested in pesticides

  • Big Business Problem: Evolution of Genetic ResistanceCreates a pesticide treadmillPesticide application

  • Benefits - Longterm?Problem: Evolution of Genetic Resistance

  • Problem: Imbalances in the EcosystemCreation of New PestsLemons

  • Alternatives to PesticidesIntegrated Pest ManagementManagement of pest not eradication

    Education of farmers

  • 1. Using Cultivation Methods

    Interplant mixtures of plantsPlanting, fertilizing, and irrigating at proper timeCrop rotationRefuge PlantingStrip or border cutting (see next slide)

  • Strip Cutting / Border Cutting

    Lygus bugs love alfalfa like cotton and hay as wellStrips 250-300 wideAlfalfa harvested in two week intervalsDrawback - Complicated irrigation and harvesting due to mix

  • 2. Resistant Crop VarietiesPlants have many natural mechanisms to keep insects at bay: repellent or toxic chemicals, thorns, hairs, and tough roots and stems.

    2. May reduce need for various cides

    3. Yields may drop since the plant puts its resources towards its defense.

    4. Evolutionary arms race continues and insects may counter plants defense.

  • 3. Natural Enemies (Biological Controls)Wasp Invaders 4 Min.

  • 4. Pheromone Traps

  • 5. Other:Alternatives to PesticidesAvoid repeated use of same pesticide

    Reproductive Controls - Sterile-male technique

    Quarantine - if foreign pest detected

    Create a refuge (no pesticide applied)

    Mechanically pull resistant weeds or vacuum bugs: non-chemical methods

  • Alternatives to PesticidesIntegrated Pest ManagementRice Production in Indonesia

  • Laws Controlling Pesticide Use

    Food, Drug, and Cosmetics Act (1938) - recognized need to regulate pesticides in food

    Federal Insecticide, Fungicide, and Rodenticide Act (1947) - regulated effectiveness of pesticides

    Pesticide Chemicals Amendment (1954) - set standards & testing for pesticides in food

    Delaney Clause (1958) - no cancer causing agent may be used

    Food Quality Protection Act (1996) - amended Delaney and reduced time to ban pesticide from 10 years to 14 months

  • Stockholm Convention

    The Global Ban of Persistent Organic Pollutants