Agricultural Methods and Pest Management

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Agricultural Methods and Pest Management

• Chapter 15

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Development of Agriculture

• Development of agriculture involved manipulating
  the natural environment to produce food desired
  by humans.
• 20,000 years ago, move seeds closer to home or
  shake seed heads to increase seed production
  following year.
• Polyculture small mixed plants, better for soil
• Labor intensive
• Hand picked insect pests
• Hand harvested
• 10,000 advent of modern agriculture in the
  fertile crescent (Tigris, Euphrates river
  junction).
• Allowed increase in the size of the human
  population.
• 75 years ago move from hand or animal labor to
  machines
• Dramatically increased acres planted
• Type of fields (no hedge rows, large tracts open)
• Chemical use also recent (since 1950s)

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Shifting Agriculture

• Typically planted with polyculture to produce
• Different microclimates
• Different nutrient mixes
• Natural insect control

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Labor Intensive Agriculture

• Favored when
• Growing site does not allow mechanization.
• Crop does not allow mechanization.
• Economic condition does not allow purchase of
  mechanized equipment.
• Most 3rd world countries except land owned by
  people from developed countries.
• Primary reason for use is economic.
• Many densely populated countries have numerous
  small farms that can be effectively managed with
  human labor.

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Mechanized Agriculture

• Typical of industrialized countries.
• Fossil fuel replaces human muscle power.
• Need large amounts of energy and flat land.
• Often use monocultures because of more efficient
  planting, cultivating and harvesting.
• Farmers often rely on hybrids to provide uniform
  monocultures.

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Problems with Mechanized Agriculture

• Large tracts of bare land increases soil erosion.
• Little genetic differentiation often leads to
  increased pesticide use.
• No crop rotation depletes soil nutrients thus
  increasing fertilizer use.
• Fossil fuel energy use has replaced human muscle
  power.

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Development of Agriculture

• Green Revolution has greatly increased worldwide
  food production.
• Introduction of new plant varieties and farming
  methods.
• Increased food production per hectare.
• Drawbacks
• Requires larger amounts of water and irrigation.
• Often requires fertilizers and pesticides.

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Increased Agricultural Yields
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Fossil Fuel Versus Muscle Power

• Labor reduction In the United States
• 1913 Required average of 135 hours of labor to
  produce 2,500 kg of corn.
• 1980 Required average of 15 hours.
• Takes 5.5 tons of fossil fuel to produce 1.1 tons
  of fertilizer.
• Developed world is dependent on oil to produce
  energy to manufacture pesticides.
• Price of oil has wide ramifications.

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The Impact of Fertilizer

• Approximately 25 of worlds agriculture crop is
  directly attributed to chemical fertilizer use.
• Fertilizers replace soil nutrients extracted by
  plants.
• Price and availability of chemical fertilizers is
  strongly influenced by worlds energy prices.

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Increasing Fertilizer Use
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Nutrients

• Primary soil nutrients often in short supply are
  Nitrogen, Phosphorus, and Potassium.
• Macronutrients - Elements used in large
  quantities. Removed after each harvest.
• Micronutrients - Chemical elements only used in
  very small quantities (boron - zinc).
• Repeated growing of the same crop may deplete
  certain micronutrients reducing crop yield.

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Nutrients

• Chemical fertilizers do not replace soil organic
  matter which is important for soil structure.
• Total dependency on chemical fertilizers usually
  reduces the amount of organic matter and can
  change the physical, chemical, and biological
  properties of the soil.

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Agricultural Chemical Use

• Pesticide - Any chemical used to kill or control
  populations of unwanted fungi, plants, or animals
  (pests).
• Can be subdivided into several categories based
  on the organisms they control.
• Insecticides - Control insect populations. - Raid
• Fungicides - Control fungal pests. Methylmercury
• Rodenticides - Control mice and rats. D Con
• Herbicides - Control plant pests. Round up
• Biocides - Control large variety of organisms. -
  DDT

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Pesticides

• Pests referred to as target organisms.
• Nontarget organisms are other organisms killed as
  an unwanted side effect.
• Persistent - Remain active for long periods.
• Non-persistent -Break down quickly.

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Insecticides

• Used to control insect populations.
• Mosquitoes are known to carry over 30 diseases
  harmful to humans.
• 3,000 yrs. ago Homer noted the use of Sulfur to
  control insects.
• Known for centuries that certain plant products
  produce repellant chemicals.
• Nicotine (tobacco)
• Rotenone (tropical legumes)

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Insecticides

• Chlorinated Hydrocarbons - Complex, stable
  structure, long-lasting, persistent pesticides.
• Effective for long periods after application.
• Tend to accumulate in soil and animal bodies.
• Affect many non-target organisms.
• No longer used in many parts of the world.
• Still used in many developing countries to
  protect crops and public health.

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Insecticides

• Organophosphates and Carbamates
• Short-lived compounds that do not persist in the
  environment, but are generally more toxic to
  vertebrates.
• Both work by interfering with the ability of the
  nervous system to conduct impulses.
• Interferes with neurotransmitters.
• Cholinesterase
• Diazinon - Sevin

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Herbicides

• Used to control unwanted plants.
• About 60 of pesticides used in U.S. are
  herbicides.
• Weeds compete with crops for soil nutrients.
• Traditional weed control methods are expensive in
  terms of time and energy.

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Herbicides Types

• Synthetic Plant Growth Regulators
• Mimic natural growth regulators (auxins).
• Photosynthetic Disruptors
• Enzyme Inhibitors

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Fungicides and Rodenticides

• Fungicides are an important defense against
  spoilage of seeds and mature crops.
• Methylmercury
• In some parts of the world, governments place a
  reward on rats because they can destroy
  agricultural crops.
• Also carry diseases harmful to humans.
• Rodenticides must be used with great care to
  prevent poisoning non-target organisms.

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Problems with Pesticide Use

• Persistence - Persistent pesticides become
  attached to small soil particles and are easily
  moved by wind or water.
• May be distributed throughout world from local
  applications.

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Problems with Pesticide Use

• Bioaccumulation and Biomagnification
• Bioaccumulation - Accumulating material within an
  organisms body.
• Many persistent pesticides are fat soluble and
  build up in fat tissues.
• Biomagnification - Acquiring increasing levels of
  a substance in bodies of higher trophic-level
  organisms.
• DDT, Mercury, PCBs
• DDT banned in U.S. in early 1970s.

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Problems with Pesticide Use

• Pesticide Resistance - Insecticides only kill
  susceptible individuals.
• Most surviving individuals have characteristics
  that allowed them to tolerate the pesticide.
• Survivors pass on genetic characteristics for
  tolerance.
• Subsequent pesticide applications become less
  effective.

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Problems with Pesticide Use

• Effects on Non-Target Organisms - Most pesticides
  are not species specific, and kill beneficial
  species as well as pest species.
• Many kill predator and parasitic insects that
  normally control pest insects.
• May change population structure so that a species
  not previously a problem may become a serious
  pest.

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Problems with Pesticide Use

• Human Health Concerns
• Acute poisoning during application.
• WHO estimates between 1 million and 5 million
  acute pesticide poisonings annually.
• Inadvertent exposure to small quantities.
• Chronic minute exposure.

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Problems with Pesticide Use

• Perfect Pesticide
• Inexpensive
• Only affect target organism
• Short half-life
• Break down into harmless materials
• Newer pesticides have fewer drawbacks than early
  hard pesticides, but none are devoid of problems.

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Why Are Pesticides So Widely Used ?

• Food Production
• Worldwide, pests destroy 35 of crops.
• Annual loss in U.S. of 18.2 billion.
• Economic Concerns
• Pesticides increase yields and profits.
• Health Reasons
• Insecticides curtail many diseases.

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Changes in Pesticide Use
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Alternatives to Conventional Agriculture

• With the development of mechanization, many
  farmers changed from mixed agriculture to
  monocultures.
• Greater opportunities for pest problems to
  develop.
• Alternative Agriculture includes all
  non-traditional agricultural methods.
• Sustainable Agriculture seeks to produce adequate
  food supplies while protecting or enhancing
  ecosystem health.

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Alternatives to Conventional Agriculture

• Organic Agriculture
• Originally, all farming was organic.
• Animal manure and crop rotation provided soil
  nutrients.
• Crop diversity prevented pest problems.
• Manual labor controlled insects / weeds.
• Some farmers are returning to organic farming due
  to chemical problems and costs.

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Alternatives to Conventional Agriculture

• Techniques for Protecting Soil and Water
• Reduce number of trips farm equipment must make
  over the land.
• Reduces soil compaction.
• Reduce fertilizer runoff.
• Careful selection, timing, and use of pesticides.
• Precision Agriculture
• Crop Rotation

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Integrated Pest Management

• IPM uses variety of methods rather than relying
  solely on pesticides.
• Requires detailed knowledge of
• Crop Plant Metabolism
• Pest - Plant Interactions
• Climatic Conditions Favoring Pests
• Encouragement of Beneficial Insects

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Integrated Pest Management

• Several methods employed
• Disrupting Reproduction
• Female Sex Pheromones
• Male Sterilization
• Natural Predators
• Aphids can be controlled with ladybugs
• Bacterial Strains

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Integrated Pest Management Methods

• Developing Resistant Crops
• Genetic Engineering (Biotechnology) involves
  inserting specific pieces of DNA into the genetic
  makeup of organisms.
• Genetically Modified Organisms
• Pest resistance
• Herbicide resistance

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Integrated Pest Management Methods

• Modifying Farming Practices
• Crop Rotation
• Selective Use of Pesticides
• Identification of precise time when pesticide
  application will have the greatest effect at the
  lowest possible dose.

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Slash and Burn

• Vegetation is cleared for agriculture and burned
  to release nutrients.
• Particularly useful on thin tropical soils.
• Cleared soil useful for 2-3 years.
• Requires a long recovery time between cycles.
• Not suitable for large, densely populated areas.