Agricultural Methods and Pest Management

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Agricultural Methods and Pest Management

• Chapter 15

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The Development of Agriculture

• Early ancestors obtained food by hunting and
  gathering
• Agriculture has developed from a need to provide
  for a growing population
• This has involved various kinds of innovations

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1. Shifting Agriculture (a.k.a. Slash and Burn)

• Cutting down and burning trees and small
  vegetation to release nutrients from this biomass
• While soil is suitable a few crops can be grown
  (2-3 years)/Then site is abandoned to allow
  forest to recolonize
• Temporary use prevents much erosion

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• Used in places with nutrient-poor soil and on
  steep slopes
• Also where human population is low, to reduce the
  size and number of these plots

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Polyculture

• Planting a mixture of crops in one garden plot
• Taller plants may help shade-requiring plants/May
  reduce insect pest problems
• Because only temporary, reduce insect infestations

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2. Labor-Intensive Agriculture

• Used when
• A) site does not allow for mechanization
• ex. mountainous regions or small plots
• B) when the kind of crop does not allow it
• ex. rice
• C) Economic condition of people (less-developed
  regions cant afford machinery)
• Ex. Many parts of Africa, Asia, and Central/South
  America

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3. Mechanized Agriculture

• Used Typical in North America, Europe and parts
  that have
• A) money and
• B) large amounts of land available
• This Requires large expenses and fairly level
  land
• Has greatly increased amount of food available

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Monoculture

• Planting of one crop on a large tract of land
• Reduces the need for change of machinery
• Drawbacks increases erosion, reduces needed
  organic matter
• Green Revolution
• Benefits Advances in agriculture have lead to
  more food production
• Drawbacks
• 1.requires use of pesticides,
• 2. more water, and
• 3. dependence on industries for specialized seeds

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Fossil Fuel vs. Muscle Power

• Mechanized agriculture requires extensive use of
  fossil fuels although food production has
  dramatically increased
• 2 factors that drastically affect food prices
• 1. Change in oil cost or
• 2. availability of fuels

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Impact of Fertilizer

• Valuable because increase soil nutrients removed
  by plants
• Three nutrients in short supply nitrogen,
  phosphorus, and potassium (Macronutrients)
• Micronutrients needed in small nutrients include
  boron, zinc, and manganese

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Agricultural Chemical Use

• Pesticide- chemical used to kill or control
  unwanted populations (fungi, animals, or plants)-
  called Pests
• Weeds-unwanted plants

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Pesticide Categories

• Insecticides- kills insect populations
• Fungicides-fungal pests that weaken plants
• Rodenticides- kill mice and rats
• Herbicides- kill weeds
• Pesticides-may also be called biocides b/c can
  kill variety of living things

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• Pest called target organism when inhibits
  specific pest
• Most pesticides not specific so they may kill
  nontarget organisms
• Persistent pesticides remain active long period
  of time
• Nonpersistent pesticides break down quickly

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Insecticides

• DDT-first insecticide used (P.334)
• It is persistent
• half-life of 10-15 yrs.
• Affected many non-target organisms

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Categories of Insecticides

• 1. Chlorinated Hydrocarbons
• Contain carbon, hydrogen, and chlorine
• Ex. DDT
• Stable-effective for long time but accumulate in
  soil and food chain
• Many no longer used b/c of negative effects

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2. Organophosphates and Carbamates

• Nonpersistent/ Decompose in hours or days
• Not species-specific
• More toxic b/c affect nervous system-uncontrolled
  spasms-result in death
• Must apply w/special equipment have training

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Herbicides

• Control unwanted vegetation
• Important since take nutrients and water from
  soil/crops need these
• Type of herbicide-Auxins- disrupt normal
  growth/death

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Fungicides

• 2 types of fungi
• 1. Decompose organic material Parasites on crop
  plants
• 2. Used as fumigants (gases), sprays, and seed
  treatments

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Rodenticides

• Rodents destroy food supplies/carry disease
• Warfarin-one of most widely used-causes internal
  bleeding in animals, even other mammals
• Must be careful

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Problems w/Pesticide Use

1. Persistence
2. Bioaccumlation/biomagnification
3. Pesticide Resistance
4. Effects on Nontarget Organisms
5. Human Health Concerns

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1. Persistence

• B/c of their stability, have become long-term
  problem
• Attach to small soil particles can be carried
  anywhere by wind or water
• Been found in the ice of the poles/ human body
  tissues

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2. Bioaccumulation/ biomagnification

• Bioaccumulation- accumulating higher higher
  amounts of material in animal bodies
• If animal w/pesticides eaten by another, then
  concentrates in that animal-leading to disease or
  death
• Biomagnification- increasing levels of substance
  in higher-trophic-level organisms (Fig. 15.9)

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3. Pesticide Resistance

• Pest populations may become resistant to
  pesticides
• Ones with characteristics that tolerate the
  chemicals may live to reproduce/their offspring
  may also posses these

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4. Effects on Nontarget Organisms

• Most are not specific/ kill beneficial species as
  well as pests (Mainly Insecticides)
• Most often becomes irreversible tactic since
  stopping my result in rapid increase of pests

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5. Human Health Concerns

• May result in short-term or long-term health
  effects
• Pesticide poisoning needing medical treatment in
  the U.S. are in the thousands per year/ World
  wide-? (many go unreported)
• Dues to improper applications/unaware of
  precautions when applying

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Contd.

• Many have been proven to cause mutations,
  cancers, abnormal births in experimental animals
• Studies of exposed farmers over years have higher
  levels of certain cancers

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Why Are Pesticides So Widely Used?

• Has increased the amount of food that can be
  grown worldwide
• The economic value farmers increase in profit
  from crops/ businesses increase from pesticide
  sales
• Control insect populations that cause many health
  problems

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Alternative Agriculture

• All nontraditional agricultural methods
• Includes the following
• Sustainable Agriculture-Seeks methods to produce
  safe food in an economically viable manner while
  enhancing health of agricultural land
• Organic Agriculture-Advocates avoiding the use of
  chemical fertilizers and pesticides

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Techniques for protecting soil and water resources

• Two problems for soil Compaction and reduction
  in organic matter
• Reduce these problems by farm equipment
  traveling less over soil (compaction) leaving
  crop residue on the soil (increases organic
  matter)

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Precision Agriculture

• Uses modern computer technology and geographic
  information systems, based on soil and
  topography, to automatically vary chemicals
  applied to the crop at different places within a
  field.
• Less fertilizer is used, and used more
  effectively.

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Integrated Pest Management

• Uses a variety of methods to control pest rather
  than pesticides alone
• Must understand all ecological aspects of the
  crops and the pests to which they are susceptible

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Disrupting Reproduction

• Pheromone- chemical released by females to
  attract males
• Spraying areas with synthetic odors confuses
  males they dont find female mates Ex. Moths
• Male sterilization- growing sterile males to mate
  with females also greatly reduces populations Ex.
  Screwworm fly

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Using Beneficial Organisms to Control Pests

• Ladybird Beetles or Ladybugs- feed on aphids
  which can destroy crops, such as orange tree
  decline in California in late 1800s
• Some insects can also control weeds
• Naturally occurring pesticides in plants help
  control pests (garlic plants-Japanese beetles)

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Developing Resistant Crops

• Genetic engineering- Inserting specific pieces of
  DNA into genetic makeup of organisms
• Known as genetically modified organisms
• A bacteria BTI produces material that destroys
  lining of insect guts, this gene has been
  inserted into several crop plants (Corn)

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Modifying Farm Practices

• Destroying crop residues to prevent overwintering
  ground for insects
• Crop rotation-planting a mixture of crops reduces
  specific insects that buildup from same crop
  being planted year after year

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Selective Use Of Pesticides

• Identifying when will have greatest impact on
  pests-reduces amount used
• Integrated pest management