Transcript Document
Chapter 13 FOOD, SOIL, AND PEST MANAGEMENT PEST MANAGEMENT PESTS AND PEST CONTROL Pest – any organism that is harmful or destructive or interferes with humans or our social or economic endeavors. Natural pest control — predators, parasites, disease organisms. In natural ecosystems In many polycultures Agro-ecosystems SOCIOECONOMIC ISSUES IN PEST MANAGEMENT Economic threshold – measure used to determine when damage caused by pest outweighs cost of applying pesticide. Insurance spraying – prevention Cosmetic spraying – used to keep fruits and vegetables looking desirable to consumers. WE USE PESTICIDES TO TRY TO CONTROL PEST POPULATIONS Pesticides Insecticides – insects killers Herbicides – weed killers Fungicides – fungus killers Rodenticides – rat and mouse killers Herbivores overcome plant defenses through natural selection; coevolution CLASSIFICATION OF PESTICIDES First-generation pesticides - natural chemicals from plants Second-generation pesticides – synthetic chemicals produced in laboratories. Paul Muller - discovered DDT would work as potent insecticide in 1939; awarded Nobel Prize in 1948 Broad-spectrum agents – toxic to many pests and non-pest species. Chlorinated hydrocarbons – DDT Organophosphates - malathion, parathion Selective or narrow spectrum agents - TERMS USED TO DESCRIBE PESTICIDES Persistence – length of time (usually years) they remain deadly in the environment and, biologically magnified in food webs Non-persistent pesticides – break down into simple nontoxic substances within a few weeks; very toxic and pose serious danger to humans. LD50 – the amount of a chemical, given all at once, which causes the death of 50% of a group of test animals. - way to measure acute toxicity of the chemical. - LD stands for lethal dose. INSECTICIDE EXAMPLES Insecticide Examples Compound Class Examples Organochlorides (chlorinated hydrocarbons) DDT, DDD, aldrin, chlordane, toxaphene, lindane Organophosphates diazinon, malathion, parathion, chloropyrifos Carbomates Carbaryl (sevin), matacil, temik, zectran, aminocarb Pyrethroids decamethrin, permethrin, bifenthrin Persistence in the Environment High 5 to 15 years Intermediate 1 week to several weeks Low2 weeks or less Lowdays HERBICIDE EXAMPLES Compound Class Examples Triazines Atrazine, cyanizine. simazine Dinitroaniline oryzalin, triflualin Phenoxy 2,4-D; 2,4,5-T; MCPB Thiocarbamate butylate, cycloate, EPTC Acidamine alachlor, propachlor INDIVIDUALS MATTER: RACHEL CARSON Biologist - noticed DDT use was increasing; mainly to control mosquitoes Silent Spring - 1962 Voiced potential threats of uncontrolled use of pesticides; especially effects of biomagnification. Gave impetus to the US environmental movement STORY OF DDT Discovered in 1930s; killed various kinds of insects. Used primarily 1940s – 1960s (WWII); to control spread of body lice on soldiers. Used in tropics to stop spread of malaria. By controlling pests, increased crop yields. Banned in US (1972) but still produced in the US. Used by many countries that export produce to the US; presence of DDT in our body tissues. PROMISES AND PROBLEMS Pests became resistant; larger amounts have to be used to get same effect. Pesticide treadmill – use of stronger and more frequent doses to be effective. Accelerate the development of resistance – 5 to 10 years sooner in the tropics. Once pests became resistant, their populations exploded. PROMISES AND PROBLEMS (CONT.) Pesticides often kill or harm non-target organisms – Kill natural predators and parasites that help control pests Predatory birds – egg shells cracked, dead chicks, lower reproductive rates. “Vanishing of the Bees”; colony collapse..??? PROBLEMS AND PROMISES Bioaccumulation – process of accumulating higher and higher doses up the trophic levels of the food chain. Biomagnification – the multiplying effect of bioaccumulation in a food chain. A substance biomagnifies when It is long-lived Producers make it more concentrated It is fat-soluble BIOMAGNIFICATION Biomagnification pyramid Chemicals such as pesticides tend to increase their concentration by approximately ten times as they move upward through the trophic levels. MODERN SYNTHETIC PESTICIDES HAVE SEVERAL DISADVANTAGES Only 0.1 - 2% of the pesticide applied by aerial or ground spraying reaches the target pest. Rest pollutes air, water, harm wild life, affect human health Persistence in nature; magnification in food chain Links to cancer, birth defects, infertility Expensive for farmers Some insecticides kill natural predators and parasites that help control the pest population Pollution in the environment Some harm wildlife Some are human health hazards MODERN SYNTHETIC PESTICIDES HAVE SEVERAL DISADVANTAGES David Pimentel: Pesticide use has not reduced U.S. crop loss to pests Loss of crops is about 31%, even with 33-fold increase in pesticide use High environmental, health, and social costs with use - $5-10 in damages for every $1 spent Use alternative pest management practices could halve the use of chemical pesticides on 40 major US crops Campbell’s soup tomatoes in Mexico, Rice in Indonesia, Sweden Pesticides industry refutes these findings GLYPHOSATE-RESISTANT CROP WEED MANAGEMENT SYSTEM: A DILEMMA Best-selling herbicide (Roundup), Monsanto Advantages – does not harm living things, degrades into harmless substances within weeks Disadvantages - resistant weeds , expensive to develop other pesticides CASE STUDY: ECOLOGICAL SURPRISES 1955 - Dieldrin sprayed to control mosquitoes Malaria was controlled Dieldrin didn’t leave the food chain Domino effect of the spraying Happy ending LAWS AND TREATIES CAN HELP TO PROTECT US FROM THE HARMFUL EFFECTS OF PESTICIDES U.S. federal agencies EPA USDA FDA Tolerance – the limit to the amount of pesticide that can remain on food. LAWS AND TREATIES FIFRA – the Federal Insecticide, Fungicide, and Rodenticide Act of 1972 Requires manufacturers to register pesticides with the EPA before marketing them and to test toxicity levels Required the reevaluation of 600 active ingredients in preexisting pesticides Allows the EPA to regulate the amount of pesticide residue on food Says EPA will consider public’s overall exposure when making decisions to set standards Allows EPA to leave inadequately tested pesticides on market; does NOT require immediate removal from market. Allows EPA to license new chemicals without full health and safety data LAWS AND TREATIES FQPA – the Food Quality Protection Act of 1996 Set standards for pesticides applied to foods (with a special concern for children). Requires that 1. 2. 3. 4. pesticide be prohibited from being used if linked to cancer. all possible exposure to pesticide be evaluated. older pesticides be reevaluated to see if they meet new standards. standards apply to both processed and raw foods. PESTICIDES AND POLICY Effects of active and inactive pesticide ingredients are poorly documented Circle of poison/boomerang effect – residues of banned chemicals exported to other countries may come back on food; winds carry persistent pesticides such as DDT US citizens contain some pesticide residue in their body tissue from pesticides that have been banned for decades INTERNATIONAL TREATIES 1998 – 50 countries developed treaty that requires exporting countries to have consent from importing countries for exports of 22 pesticides , 5 industrial chemicals 2000 – 100 countries signed to phase out 12 of the most hazardous persistent organic pollutants (POP’s), 9 of them hydrocarbons (DDT) United States has not signed this agreement HOW CAN WE PROTECT CROPS FROM PESTS MORE SUSTAINABLY? We can sharply cut pesticide use without decreasing crop yields by using a mix of cultivation techniques, biological pest controls, and small amounts of selected chemical pesticides as a last resort. IPM INTEGRATED PEST MANAGEMENT IS A COMPONENT OF SUSTAINABLE AGRICULTURE Integrated pest management (IPM) Coordinate cultivation, biological controls, and small amounts of selected chemical pesticides to reduce crop damage to an economically tolerable level. Disadvantages Expert knowledge What works in one area may not work elsewhere NATURE CONTROLS THE POPULATIONS OF MOST PESTS – “OPERATION CAT DROP” ALTERNATIVES TO USING PESTICIDES Fool the pest : rotate crops, adjust plant times Implant genetic resistance - GMO’s; genetic control Bring in natural enemies; natural predators (biological control) Use hormones/insect perfumes (pheromones) Genetic controls Cultural control OTHER ALTERNATIVE PEST CONTROL METHODS 1. Biological control - using natural enemies, or predator bugs, to control pests. 2. 3. Pheromones - chemicals that a species emits to attract members of the same species. Scientists use these pheromones to trap pests in devices baited with poison. Genetic control - breeding plant varieties that are resistant to pests. 4. For example, ladybugs can be purchased at most garden stores to help control aphids, a common garden pest. Must be careful – controls may also attack beneficial species. For example, plants can be bred to produce chemical barriers that kill or repulse pests. Another example is to release a group of sterilized males into the environment. These sterilized males mate with females, which prevents future attempts for the female to mate. Cultural control - where the environment is altered in such a manner that pests cannot thrive. Changing bed linens to prevent bedbugs or cleaning the house to prevent roaches are examples. WHAT IS MEANT BY “ORGANIC” ? Organic foods - grown with little or no pesticides, chemical fertilizers, antibiotics, or hormones. BUT, according to United States Department of Agriculture – must use organic fertilizer and pheromones to disrupt insect mating cycle. Organic farming produces smaller yields than nonorganic farming methods. However, sales of organic foods have increased by 20% each year for the past 10 years.