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Chapter 20

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  1. Chapter 20 Protecting Food Resources: Pesticides and Pest Control

  2. Rachel Carson was a scientist who wrote Silent Spring in 1962. • It addressed the growing use of pesticides (DDT) and their unpredicted effects on song birds. • Original users of pesticides did not know that the poisons used to kill insects would accumulate in other living things and kill them too. BIOACCUMULATION

  3. Pesticides: Types and Uses What is a Pest? • A pest is any species that competes with us for food, invades lawns and gardens, destroys wood in houses, spreads disease, or is simply a nuisance • Most of the time nature takes care of the pests through natural enemies (predators, parasites, and disease organisms)

  4. So what’s a Pesticide? • Pesticides (also known as biocides) are chemicals that are to kill organisms we consider undesirable • Insecticides • Herbicides • Fungicides • Nematocides • Rodenticides

  5. Above: Worker prepares his vehicle for a day of pesticide spraying

  6. Coevolution For almost 225 million years, plants have been producing chemicals to ward off or poison herbivores that feed on them… But, through what is known as coevolution, the predators overcome various plant defenses by natural selection and the plants must develop new defenses

  7. First Attempts at Pesticides • Sulfur (early 500 BC) • Toxic compounds of arsenic, lead, and mercury (1400’s) • Abandoned in late 1920’s when the increasing number of human poisonings increased • Nicotine Sulfate (1600’s) • Pyrethrum and Rotenone (mid-1800’s)

  8. Paul Mueller and the Second Generation In 1939 Paul Mueller discovered that DDT, a chemical known since 1874, was in fact a potent insecticide. DDT became the first pesticide of the so-called Second GenerationPesticides. Mueller went on to win the Nobel Prize in 1948 for his discovery.

  9. Pesticides Today • Chemists have been developing hundreds of synthetic organic chemicals for use as pesticides • Worldwide about 2.3 million metric tons of pesticides are used yearly • 1 lb for each person on earth • 75% in developed countries (Latin America, Asia and Africa on the rise) • 1996 world sales = $30 billion($11 billion: US)

  10. Here in the US • About 630 different biologically active (pest killing) ingredients and about 1,820 inert (inactive) ingredients are mixed to make some 25,000 different pesticide products in the United States

  11. Resistance to pesticides • Some individuals are genetically immune to a pesticide. • They survive and pass these genes to their offspring. • Pesticides stop being effective.

  12. Pesticide Distribution in US • Cultivation of two crops • Cotton (55%) • Corn (35%) • Used about 90% of the insecticides and 80% of the herbicides applied to crops in the United States in 1995

  13. Example of Solid Pesticides

  14. More Distribution • 25% of the pesticide use in the United States is for ridding houses, gardens, lawns, parks, playing fields, swimming pools, and golf courses of unwanted pests • Average lawn in US = 10x’s more pesticides per hectare than US cropland • Each year = 250,000 residents become ill

  15. Biological control • Biological control (Biocontrol): uses a pest’s natural predators to control the pest • Leads to steep reductions in chemical pesticide use • Cactus moths control invasive prickly pear cactus • Bacillus thuringiensis (Bt): soil bacteria that kills many pests

  16. Biocontrol involves risks • No one can predict the effects of an introduced species. • The agent may become invasive and harm non-target organisms. • Cactus moths are eating rare Florida cacti. • Removing a biocontrol agent is harder than halting pesticide use. • The harm done by biocontrol agents may be permanent.

  17. Some Quick Facts • Broad-Spectrum agents : toxic to many species • Selective or Narrow spectrum agents : effective against a narrowly defined group of organisms • Pesticides vary in persistence (length of time they remain deadly in environment)

  18. The Pros • Pesticides save human lives: has prevented premature births due to malaria, bubonic plague, typhus, sleeping sickness (all carried by pests) • Pesticides increase food supplies and lower food costs: 55% of crop lost before harvest due to pests • Pesticides increase profits for farmers: every $1 spent on pesticides yields worth approximately $4 (although dropped to $2 if harmful effects)

  19. More Pros • Pesticides work faster and better than alternatives: Pesticides can control pests quickly and at a reasonable cost. Long shelf life and easily shipped and applied • Health risks insignificant when compared to their benefits • Safer more effective pesticides are being developed • New pesticides are being used in less rates per unit when compared to older products

  20. Ultimate Goal of Pesticides • Kill only the target pest • Harm no other species • Disappear or break down into something harmless after doing its job • Not cause genetic resistance in target • Be cheaper than doing nothing

  21. The Cons • Genetic Resistance: pest organisms develop resistance to the pesticide after a short period of being exposed to it • Broad-Spectrum insecticides kill natural predators and parasites that may have been maintaining the population of a pest species at a reasonable level • Ex. Wolf spiders, wasps, predatory beetles…

  22. Cons continued… • Because natural predators can be wiped out; this may unleash new pests whose populations the predators had previously held in check

  23. In Our Water • Testing in rivers and water reveal that pesticides have strayed away from there targets and found there way into the waters

  24. Pesticide Treadmill • As pests become resistant to the pesticides, sales reps for the pesticide recommend larger doses or more frequent application • As a result farmers end up on a pesticide treadmill where they end up paying more and more for a pest control program that often becomes less and less effective

  25. Pesticide Treadmill • Pesticides become less effective over time • Genetic resistance to pesticides develops in pest species – natural selection • Some individuals have a gene that makes them resistant to a pesticide, they pass the gene onto their offspring so that the entire population becomes resistant • This requires a more frequent sprayings, larger doses or a switch to new pesticides • Yields have decreased because of pesticide resistance since second generation pesticides have come into use

  26. Example of Pesticide Treadmill In Central America, cotton growers increased the frequency of insecticide applications from 10 to 40 times per growing season. Still, declining yields and falling profits forced many of the farmers into bankruptcy

  27. Insecticide application Chromosome with gene conferring resistance to insecticide Survivors Additional applications of the same insecticide will be less effective, and the frequency of resistant insects in the population will grow Figure 13.1

  28. Where does it all go? • Only about 2% of the sprayed insecticide by air reaches target pests • Less than 5% of herbicides applied reach target weed • Pesticides that don’t reach there target end up in the air, surface water, groundwater, bottom sediments, food and other non-target organisms

  29. Continued • Still, pesticide waste can be reduced by using re-circulating sprayers, covering spray booms, and using rope-wick applicators

  30. DDT • Banned in 1972 by US • 1980 high levels in peregrine falcon and the osprey • EPA found DDT in 99% of the freshwater fish it tested • DDT drifts from other countries still using it

  31. DDT accumulates in fat body tissues of animals • DDT was not used for handling weeds • DDT is, persistent, synthetic organic compound and a subject to biomagnifications in food chains

  32. World’s Worst Industrial Accident • Bhopal, India • Occurred December 2, 1984 • Union Carbide (a pesticide manufacturer) • MIC (methyl isocyanate) gas leaked • the cooling system malfunctioned and the tank exploded • Gas affected 30 square miles and an estimated 600,000 people were exposed

  33. Bhopal • Officially 5,100 people were killed (probably anywhere from 7,000 – 15,000 died) • 50,000 – 60,000 sustained permanent injuries, blindness or lung injuries

  34. The Cause? • Indian government claims it was caused by company negligence • The company claims sabotage by a disgruntled former worker

  35. Regulation in the US • All commercial pesticides must be approved by EPA • EPA reviews each pesticide • EPA sets tolerance levels : amount of toxic pesticide residue that can legally remain on crop • No longer has to test on birds and fish • 55 active pesticides banned in US, but may be used and shipped elsewhere

  36. More Regulations • National Academy of Sciences says that the federal laws are not adequate • 98% of potential risk of cancer would be eliminated if pesticide residue on food eliminated by government • Approximately $1 Billion spent on regulating pesticides each year

  37. FIFRA and the EPA • Federal Insecticide, Fungicide, Rodenticide Act • All commercial pesticides must be approved for use • The pesticide companies evaluate the biologically active ingredients in their products and the EPA reviews the data • When a pesticide is approved for use on fruits or vegetables, a tolerance level is set that can legally remain on a crop when a consumer eats it

  38. 1996 Food Quality Protection Act • Requires food to have only reasonable levels of pesticide tolerance • It requires manufacturers to demonstrate that the active ingredients in there products are safe for infants and children • Requires EPA to consider exposure to more thatn one pesticide when setting pesticide tolerance levels • EPA develops program to screen ingredients

  39. From Above • Just one of the many ways that pesticides are being applied are through aerial drops of the chemicals

  40. Other Solutions • Crop rotations • Planting times can be adjusted • Plowing at night (reduces weeds) • Plant where major pests do not exist • Switch away from monoculture to intercropping, agroforestry, and polyculture

  41. More Solutions • Plants and animals that are genetically resistant to certain pest insects, fungi and diseases can be developed - downside: costly • Biological control: predators and pathogens • 300 biological pest control successful in China and Cuba • Biological Control: non-toxic to humans • Downside: timely

  42. We depend on insects to pollinate crops • Most insects do not harm agriculture, and some are absolutely vital. • 800 cultivated plant species rely on insect pollinators. • Pollination: male plant sex cells (pollen) fertilize female sex cells • By wind or animals • Pollinators include: • Hummingbirds • Bats • Insects

  43. Colony Collapse Disorder • Populations of native pollinators have plummeted. • Honeybees pollinate more than 100 crops — 1/3 of the U.S. diet. • Recently, introduced parasitic mites have devastated hives. • To conserve pollinators: • Reduce or eliminate pesticide use • Plant gardens of flowering plants

  44. Even more Solutions… • Plant toxins • Bt toxin used to kill thousands of strain of common soil bacterium • Insect Birth Control (sterile male approach) • Aqua heat: spray boiling water on crops

  45. Fish or frankenfish? FDA weighs altered salmon

  46. Yes… more solutions • Some crops can be exposed to gamma rays after harvest • Extends shelf life • Critics say irradiating food destroys vitamins and other nutrients • Increases death from botulism poisoning • Picowaved stickers on food that has been

  47. Integrated Pest Management (IPM) • IPM uses multiple techniques to suppress pests. • Biocontrol • Chemicals, when necessary • Population monitoring • Habitat alteration • Crop rotation and transgenic crops • Alternative tillage methods • Mechanical pest removal

  48. Integrated Pest Management (IPM) • Each specific crop and its pest(s) are evaluated • It requires a mix of biological, cultivation and chemical practices • Pests populations are not eradicated, but carefully managed so that crop destruction is minimized

  49. IPM • Biological methods – predators, parasites, disease organisms, sterilization, sex attractants, hormones • Cultivation – vacuuming, planting times, trap crops, polyculture, intercropping, agroforestry • Development of genetically resistant plants, genetically engineered plants • Chemical pesticides in small amounts are used as a last resort

  50. IPM • Integrated Pest Management • Goal is reduction of crop damage to an economically tolerable level • Carefully monitor damage levels of pests • When reached, farmers first use biological methods • Small amounts of insecticides are used as a last resort