PROTECTING FOOD RESOURCES: PESTICIDES AND PEST CONTROL

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CHAPTER 16

• PROTECTING FOOD RESOURCES PESTICIDES AND PEST
  CONTROL

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What good is a spider?

• Chinese farmers are fighting insect pests with
  their naturally evolved natural enemies -the
  spiders
• How are they encouraging the spiders?
• Only a few species are actually dangerous to
  people
• If bugs inherit the earth, we need to have their
  predators - the spiders -on our side!

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Pesticides Types and uses

• What are pests?
• They compete with us for food
• they invade lawns and gardens
• they destroy wood in houses
• they spread disease
• they are a nuisance
• By simplifying ecosystems we have eliminated many
  natural predators

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Pesticides Types and uses - 2

• What are pesticides?
• Insecticides - kill insects
• Herbicides - kill weeds
• Fungicides - kill fungi
• Nematocides - kill roundworms
• rodenticides - kill rats and mice
• Plants and herbivores have co-evolved chemical
  defenses against each other for years

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First generation of pesticides and repellents

• First sulfur, then in 1400s toxic compounds of
  arsenic, lead and mercury were put on crops - but
  caused human poisonings
• Then compounds extracted from plants - nicotine
  sulfate, pyrethrum, rotenone
• ant repellents boric acid, vinegar, cayenne
  pepper, and mint leaves
• mosquito repellents - basil, vinegar, lime juice,
  mungwort oil - not bug zappers

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First generation of pesticides and repellents - 2

• Repel cockroaches - boric acid and banana spiders
  and trapping roaches
• Repel flies - grow basil tansy flypaper
• Repel fleas - flea soaps, feed brewers yeast and
  Vitamin B, flea powders and dips.
• Higher lawns, not closely cut, provide spider
  habitats

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Second general of Pesticides

• 1939 - DDT discovered followed by other
  synthetic organic chemicals
• Use by homeowners has grown has led to problems
  such as poisoning
• These may be broad spectrum agents or more
  selective narrow spectrum agents
• They vary in persistence

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The case for pesticides

• They have saved lives
• They increase food supplies and lower costs
• They increase profits for farmers
• They work faster better than alternatives
• Benefits exceed health risks - when used properly
• Safer pesticides are being developed and new ones
  are used at low rate

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The case against pesticides

• Development of genetic resistance
• Broad spectrum insecticides kill natural
  predators and parasites of pests
• Without predators, new pests, previously in
  check, may become prevalent

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Pesticide treadmill

• Genetic resistance --gt using more pesticide, more
  frequently, and switching to new pesticide
• Alternative pest control practices are needed
• Decrease in pesticide use would cut food costs
  and increase farmers income
• Successes Sweden Campbells soup in Mexico

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Where do pesticides go?How do they harm wildlife?

• With aerial and ground spraying only 2-5 reaches
  target weeds
• Better to use recirculating sprayers, cover spray
  booms to reduce drift, or use rope-wick
  applicators genetically altered crops

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How do insecticides harm wildlife?

• Biological magnification --gtweak egg shells
• Illegal use of banned pesticides
• Honeybees and fish are threatened

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Pesticides threaten human health

• Underestimate of health effects among farm
  workers due to poor records, few doctors
  reporting, and faulty diagnoses
• Problems due to inadequate education, poor
  warnings, lax/nonexistent regulations and lack of
  protective equipment
• DDT replaced by organophosphate pesticides - less
  persistent but more toxic

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Pesticides threaten human health-2

• Degree of illegal pesticide use is not known
• Pesticide residues in food is carcinogenic
• Increasing concern about
• genetic mutations
• birth defects
• nervous system disorders (behavior disorders)
• immune and endocrine system effects

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Pesticide regulation in U.S.

• Is the public protected by FIFRA and EPA?
• Evaluate biologically active ingredients
• Less than 10 evaluated fully
• Set tolerance level - safe level for crop use
• Banned most chlorinated hydrocarbon insecticides,
  several carbamates and organophosphates and
  systemic herbicides
• Premature deaths due to exposure underestimated

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Other ways to control pests

• Controlling pests with cultivation practices
• crop rotation and poly vs. monocultures
• planting barriers e.g. hedges to hinder insects
• plant where pests dont exist or at a time when
  they are not prevalent
• plant trap crops and remove infected plants
• use plastic or vacuum off insects
• Traditional cultivation made use of many of these
  practices abandoned with modern methods

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Genetically resistant plants losses

• Conventional methods of crossbreeding to get
  stronger, more disease (and pest) resistant
  plants is expensive and time-consuming.
• Genetic engineering is speeding up the process.
• Why would biotech companies be focusing on
  developing strains resistant to herbicides rather
  than to reduce need for pesticides?

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Natural enemy used for pest control

• Biological pest control uses predators, parasites
  and pathogens
• e.g. parasitic wasp use in Nigeria
• cost effective - spend 1 - save 25 in damage
• Advantages
• focus on selected target species nontoxic on
  others
• once established, may be self-perpetuating
• minimal development of genetic resistance

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Natural enemy used for pest control-2

• Limitations
• years of research required to understand
  ecological interactions - to choose best agent
• biological agents difficult to mass produce
• may be difficult to apply and act slowly
• biological agents must be protected from
  pesticides used nearby
• may cause unpredicted harmful effects

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Use of biopesticides

• Botanicals (chemicals from plants)
• Microbes like Bacillus thuringensis toxin
• used frequently by organic farmers
• but genetic resistance is occurring

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Insect birth control methods

• Process involves
• Raise male of insect pests in laboratory
• Sterilize them with radiation or chemicals
• Release for mating with fertile females
• Problems with approach
• high costs
• mating times and behaviors difficult to learn
• need large of sterile males
• works on limited of species

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Phermone control methods

• Chemical sex attractant secreted by females ready
  to mate useful because chemicals
• attract only one species
• work in trace amounts
• cause little genetic resistance
• not harmful to nontarget species
• But it is costly and time-consuming to identify,
  isolate and produce sex attractants
• Hormones can interrupt life cycles

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Zapping insects

• Zap with hot water - cost equals chemicals
• Zap foods after harvest with radiation
• effective against insects, parasitic worms and
  bacteria
• food does not become radioactive
• potential benefits exceed risk
• more study needed
• loss of vitamins minerals
• danger to irradiation workers
• botulism

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Integrated Pest Management -IPM

• Each crop and its pests are evaluated as parts of
  an ecological system
• Aim is reduction of crop damage - not elimination
  of pest population
• First use methods on p. 421 then try botanicals
  if necessary

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Integrated Pest Management -IPM

• Indonesia banned many pesticides, ended pesticide
  subsides, started IPM education program
• Dramatic results
• 65 decrease in pesticide use
• 15 increase in rice production
• 250,000 farmers trained in IPM
• saved 120 million/year pesticide subsidies -
  1.2 billion total saved by government
• similar results in China, U.S, Australia, Brazil

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Integrated Pest Management -IPM

• Limitations
• IPM requires expert knowledge pest situation
• Slower acting than conventional pesticides
• Methods may vary from situation to situation
• Hindered by current government subsidies of
  chemical pesticides
• Few county farm agents trained in IPM
• 5 suggestions made to promote IPM in U.S.