Presentation on theme: "C HAPTER 16 P ESTS AND P EST C ONTROL Environmental Science."— Presentation transcript:
C HAPTER 16 P ESTS AND P EST C ONTROL Environmental Science
L EARNING O BJECTIVES Define pest Why do we control pests? What are the methods to control pests and the philosophies of pest control? What are the problems with pesticides? Define Integrated Pest Management, is it successful? Any current revisions? How are exportations to developing countries regulated? How are importations of food to our country regulated?
V OCABULARY Pest: any organism that is noxious, destructive, or troublesome Agricultural pests Insecticide – toxin aimed at killing insects Herbicide – toxin aimed at killing plant or fungus Pesticide – toxin aimed at killing all pests
PHILOSOPHIES OF PEST CONTROL Chemical Treatment: Ecological Control: long-lasting protection Against pest or ecosystem Integrated Pest Management First generation pesticides: toxic heavy metals Second-generation pesticides: synthetic organic chemistry
DDT: PART 1 1940s – 1950s General Consensus at the time: Toxic to insects and NOT to humans Broad spectrum, kills all types of insects, but relatively low risk to mammals Persistent (sticks around without degradation) Saved many lives during WWII to prevent spread of body lice and death from typhus fever (sores, ab pain,deliria); also used in tropics to stop the spread of malaria by mosquitoes Used to increase crop production by controlling insect pests in agriculture
DDT Part 1 (continued) History of DDT: DDT ( d ichloro d iphenyl t richloroethane) is one of the most well-known synthetic pesticides 1874 - synthesized 1939 - DDT's insecticidal properties discovered, where it kills by opening sodium ion channels in the neurons, causing them to fire spontaneously leading to spasms and eventual death used with great success in the second half of World War II to control malaria and typhus among civilians and troops after the war, DDT was made available for use as an agricultural insecticide, and soon its production and use skyrocketed. 1948 - Swiss chemist Paul Hermann Müller was awarded the Nobel Prize in Physiology or Medicine "for his discovery of the high efficiency of DDT as a contact poison against several arthropods.“
DDT: P ART 2 Decline of birds on top of food chain (osprey, eagles) Eggs breaking before hatched Bioaccumulation: synthetic organics and breakdown products trapped in body’s lipids Biomagnification: multiplying affect of bioaccumulation as you move up food chain, negative in this case Pg. 423
DDT Part 2 (continued) 1960s - today 1962, Silent Spring by American biologist Rachel Carson was published, cataloguing the environmental impacts of the indiscriminate spraying of DDT in the US and questioned the logic of releasing large amounts of chemicals into the environment without fully understanding their effects on ecology or human health.Silent Spring The book suggested that DDT and other pesticides may cause cancer and that their agricultural use was a threat to wildlife, particularly birds. Its publication was one of the signature events in the birth of the environmental movement, and resulted in a large public outcry that eventually led to DDT being banned in the US in 1972.environmental movement DDT was subsequently banned for agricultural use worldwide under the Stockholm Convention, but its limited use in disease vector control (like malaria) continues to this day and remains controversial.disease vector the US ban on DDT (and Endangerd Species Act of 1973) is cited by scientists as a major factor in the comeback of the bald eagle from near- extinction in the contiguous US.
P ROBLEMS WITH CHEMICAL PESTICIDES Since the plant eating insects (the “pests”) are part of a dynamic ecosystem, Chemical treatments of crops can lead to pesticide treadmill as seen on page 418 Pest problem surpasses economic threshold use chemical pesticides surviving pests develop resistance to that dosage leading to resurgence of stronger pests Thru biomagnification of pesticide effects the predator insects are killed off more than actual pest allowing for resurgence AND secondary outbreaks (when other plant eating insects previously not “pests” become pests due to having no predators higher and more severe pest problem leads to ever-increasing dosages of pesticides and dependence on them more contamination of food stuffs and ecosystem….YUCK Human Health Effects Poisoning (toxin)? Cancer (carcinogenic)? Birth Defects (teratogen) Endocrine Disruptors like atrazine and alachor weed killers. (increased breast cancer and defective or low sperm counts, other sexual abnormalities)
Solution: nonpersistent pesticides or IPM Toxicity through biomagnification up food chain Broad effect on unintended organisms (like us) Location of application (in a riparian environmental, a watershed or upwind) Effect on beneficial insects Persistent: take a long time to break down – esp. chlorinated hydrocarbons, long-range danger and long term Environmental Effects of Chemical Pesticides
NONPERSISTENT PESTICIDES Since persisent pesticides are banned now, Agrochemical industry has created nonpersistent organic phosphates (malathion, parathion, chlorpyrifos) and carbamates (aldicarb and carbaryl) Typically inhibit enzyme cholinesterase essential for proper functioning of nervous system in insects, and all animals (us too) Dangers: Persistent enough to ride the food supply from farmer to consumer (few weeks to break down) Many are more “toxic” to mammals than older chlorinated hydrocarbons varieties like DDT (higher LD 50 ) and require more applications (higher dosage) Still kill beneficial insects and have biomagnification effect see Argentina Hawk problem pg 421
4 Categories of natural or biological PEST CONTROL 1. Cultural: nonchemical alteration of environmental factors (import restrictions, grass lawn of at least 3 inches high keeps away most crabgrass & noxious weeds, crop rotation) 2. Control by natural enemies/predators (parasitic wasp uses gypsy moth pupa or tomato hornworms, or less pesticide spraying to allow natural return predators to control brown planthoppers on rice) 3. Genetic Control: Chemical Barriers (crossbreeding of plants to enhance toxic chemical production by plant like with Hessian fly and wheat leaves) Physical Barriers (hooked sticky hairs on stems to trap small larva)
4 Categories of natural or biological PEST CONTROL 3. Genetic Control (cont.): Sterile Males so no successful offspring Biotechnology to introduce genes from bacteria, virus or other plant species (GMO’s like engineering Bt, a bacillus thuringienis protein, into plants which kills larva of plant eating insects,but harmless to mammals & birds) (Roundup herbicide resistant gene in crops, 90% of US soybean crop is “Roundup Ready”) 4. Natural Chemical Controls Use of hormones (chemical signals) like pheromones to cause physiological issues or stunt development cycle (Juvenile hormone prevents pupation, or Mimic emulates ecdysone hormone causing molting to begin but not finish
Integrated Pest Management (IPM) Coordinated use of pest & environmental information to develop the best feasible control methods, often using natural pathways to promote sustainable control when possible In a way that is the least harmful to people, property and environment and still cost effective Emphasis is on pest “control” not eradication Targeted, finely tuned common-sense methods as opposed to indiscreminate toxification of EVERYTHING A return to old-school, pre-chemical industry methods of pest management 4 Tiered Approach: Pest Action Threshold, Information Building, Prevention First, Control and Reduction (biological first, then narrow range synthetic, then broad spectrum synthetic (see IPM Notes ppt for more details)
Concerns when regulating pesticide Evaluated for intended use and impacts on environmental health Proper training and safety of agricultural workers using it Risk of pesticide residue on our food
PUBLIC POLICY (pg 432 & 433) FFDCA 1938 (Federal Food, Drug, and Cosmetic Act) is a piece of legislation that first started the control pesticide residues left on food eaten in the US; the “Delaney Clause” was controversial because it prevented any trace of a pesticide that had evidence of being carcinogenic in lab animal tests (too restrictive?) 3 agencies involved: EPA sets allowable tolerances FDA monitors and enforces all food except meat while USDA (US Dept of Ag) enforces meat, poultry and eggs FIFRA 1947 & 1972 (Federal Insecticide, Fungicide, and Rodenticide Act) Must register pesticide, label lists active ingredients FQPA 1996 (Food Quality Protection Act) The new law regulating safe amounts of pesticide residue on food, requiring “reasonable certainty of no harm, especially in chronic cause of cancer or exposure to children” Developing Countries and Importing Foods Prior informed consent (PIC) managed by FAO – importers and exporters inform each other of practices
N EW P OLICY N EEDS Reduction of pesticide use Develop methods that rely on biological control and use of natural processes Adopt IPM practices Adopt “precautionary principle” (like European Union has) of requiring burden of proof on manufacturers not consumers, meaning a new chemical must be proven safe rather than assumed safe until long term problems develop
DDT DDT was not used for handling weeds but has saved millions of lives by controlling disease-causing pests The 1948 Nobel prize was awarded to Paul Muller for discovering DDT DDT is a cheap, persistent, synthetic, organic, compound & is subject to biomagnifications in food chains
D ISEASES Lyme disease can be transferred to humans through a bite from an infected tick (vector) Mosquitoes are the vector for Malaria The protozoan of the genus Plasmodium is the causative agent of malaria DDT is great at killing mosquitoes… should we use it? Lack of access to safe drinking water is a major cause of disease transmission in developing countries.