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Chapter 22. The Pesticide Dilemma. http://smccd.net/accounts/snitovsky/bio215/Labs/bioins.html. Pesticides. Pesticides : toxic chemicals used to control pests (weeds, rodents, insects, bacteria, fungi…) Herbicides weeds Rodenticides rats, mice, moles, voles
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Chapter 22 The Pesticide Dilemma http://smccd.net/accounts/snitovsky/bio215/Labs/bioins.html SACCONE POWERPOINT
Pesticides • Pesticides: toxic chemicals used to control pests (weeds, rodents, insects, bacteria, fungi…) • Herbicides weeds • Rodenticides rats, mice, moles, voles • Insecticides insects, arachnids • Fungicides fungi, molds, yeasts http://www.epa.gov/ebtpages/pollchemicals.html SACCONE POWERPOINT
Narrow-Spectrum • These pesticides would kill only the target organism. • It would biodegrade into C, H, & O. • It also would not move throughout the environment. • However this “perfect pesticide” does not exist. SACCONE POWERPOINT
Broad-Spectrum • These pesticides kill a wide variety of organisms, including beneficial ones. • They do not readily break down but they turn into secondary pollutants. • They also move easily through ecosystems & biomes (mobile). SACCONE POWERPOINT
Pesticides • 1st Generation Pesticides: produced prior to 1940 (before synthetics) & include inorganics, organics, & botanicals. • Botanicals are plant derived pesticides that are produced as a natural plant defense. • Ex: nicotine (tobacco), pyrethrin (chrysanthemum), rotenone (Derris plant) SACCONE POWERPOINT
Pesticides 2nd Generation Pesticides: synthetic (man-made) pesticides mostly used after the 1940’s. Ex: DDTdichloro-diphenyl-trichloroethane was the first of the 2nd generation pesticides (1939). SACCONE POWERPOINT http://www.epa.gov/pesticides/about/types.htm
Major Groups of Insecticides • Chlorinated hydrocarbons: Organic compounds that contain Cl. • These are mostly broad-spectrum pesticides. Slow degradation & remain in the environment & within organisms. • Still in use; endosulfan, lindane, & methoxychlor. • 1963 author Rachel Carson brought pesticides to the public attention in Silent Spring.
Major Groups of Insecticides • Organophosphates: These contain phosphates & were developed based upon nerve gas..; These are more poisonous than other insecticides. They are toxic to birds, bees, & aquatic organisms. • These don’t persist in the environment as long as the Hydrocarbons. Have replaced commercial use of hydrocarbons. • Ex: Methamidophos, dimethoate, & malathion. http://www.crisny.org/not-for-profit/nycap/mosquitopaper.htm SACCONE POWERPOINT
Major Groups of Insecticides Carbamates: derived from carbamic acid. Are broad-spectrum pesticides. Not as toxic to mammals as organophosphates. Ex: carbaryl & aldicarb SACCONE POWERPOINT
Major Groups of Herbicides • Nonselective: Kill all vegetation. • Selective herbicides: kill only certain types. A) Broad-leaf herbicides: Kill broad-leafed plant but no grasses. B) Grass Herbicides: kill grass but safe for most other plants. SACCONE POWERPOINT
Use of Herbicides in Vietnam SACCONE POWERPOINT
Use of Herbicides in Vietnam • 12 million gallons of herbicides to expose hiding places & destroy crops of Vietcong. Agent White, Agent Blue, and Agent Orange. • Agent Orange is made of: (2,4,-D) 2,4 dichlorophenooxyacetic acid & (2,4,5-T) 2,4,5 trichlorophenooxyacetic acid as well as dioxins. Birth defects, stillbirths, cancer in Vietnam Agent orange Syndrome in Vietnam Vets.
Benefits of Pesticides • Disease control (malaria, west Nile) • Crop protection (increase yields) SACCONE POWERPOINT
Problems with Pesticides • Genetic resistance • Imbalance in the ecosystem • Persistence of pesticides • Bioaccumulation in organisms • Biological magnification in food web • Mobility in the environment • Risks to human health (short-term & long-term) SACCONE POWERPOINT
Problems with Pesticides • Genetic resistance: inherited characteristics (natural selection) that decrease the effect of the pesticide on the pest. • Resistance Management: a technique employed to delay the evolution of genetic resistance in a population to maximize the effectiveness of a pesticide. Methicillin-Resistant Staphylococcus aureus Infections http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5233a4.htm
Problems with Pesticides • Imbalance in the ecosystem http://www.indiana.edu/~bradwood/eagles/ddt2.htm
Problems with Pesticides DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane) are chemicals similar to DDT that contaminate commercial DDT preparations. DDE has no commercial use. DDT Eagles DDE DDD was also used to kill pests, but its use has also been banned. One form of DDD has been used medically to treat cancer of the adrenal gland.
Imbalance in the ecosystem SACCONE POWERPOINT
Problems with Pesticides http://www.epa.gov/pbt/pubs/accomp99.htm • Persistence: resistance to degradation into less toxic forms.
Biological magnification Bioaccumulation
Problems with Pesticides • Bioaccumulation: the build up of a persistent chemical (pesticide)within an organism.
Biological magnification: an increase in the chemical (pesticide) concentration of a pollutant as it passes through successive trophic levels of a food web.
Problems with Pesticides • Mobility in the environment
Pesticide Mobility in the environment SACCONE POWERPOINT
Problems with Pesticides Risks to human health Short-term: Poisoning & irritation Long-term: Cancers Endocrine disruption Mental/physical retardation
Solutions to the Pesticide Dilemma • Using cultivation to control pests • Biological controls • Pheromones & hormones • Genetic controls • Bt & its potential & problems • Quarantine • Integrated Pest Management • Irradiating Foods
Solutions to the Pesticide Dilemma • Aphid infestation of Wheat & Barley • Infestation was stopped by a local resistant variety of these plants (not a monoculture.) • Using cultivation to control pests
Solutions to the Pesticide Dilemma • Biological controls: utilizes naturally occurring disease organisms, parasites,, or predators to control pests. • Sterile Male technique: reduces population by “tricking” the females into thinking their eggs have been fertilized (sterile male can’t)
www.ces.ncsu.edu/.../notes/ Fruits/NoteS-1.html biological controls • Aphids and Ladybeetles
Solutions to the Pesticide Dilemma • Hormones: chemical messengers produced by organisms. • Pheromones: reproductive hormones used to lure in the opposite sex. • Both are used to lure pests into traps or to confuse pests to prevent mating.
Solutions to the Pesticide Dilemma Scientists will use pheromones to kill sea lamprey
Solutions to the Pesticide Dilemma • Genetic controls: using genetic variation to produce species that are resistant to pests. • Selective breeding (genetic diversity) Or • Genetic engineering: the ability to take one gene from an organism & place it into an unrelated organism where it is expressed.
Solutions to the Pesticide Dilemma • Case in Point: Bt, Its Potential & Problems http://www.bt.ucsd.edu/crop_refuge.html
Solutions to the Pesticide Dilemma • Quarantine: restricting the importation of exotic plant & animal material that might harbor pests.
Solutions to the Pesticide Dilemma • Integrated Pest Management
Solutions to the Pesticide Dilemma http://www.storewars.org/flash/index.html • Irradiating Foods:
www.ext.vt.edu/pubs/foods/ 458-300/458-300.html Irradiating Foods
Pesticide Dilemma: Laws, Laws, Laws • FDCA Food, Drug, and Cosmetics Act: enacted in 1938 it recognized the need to regulate pesticides in food (no means for regulation) The Miller Amendment: passed in 1954, required standards for levels of pesticides in food (acceptable & unacceptable) Who decides? Criteria? The Delaney Clause: 1958, no known carcinogens (lab animals or humans) would be permitted in processed foods. (based upon 1978 standards) Prior?
Pesticide Dilemma: Laws, Laws, Laws • FIFRA: Federal Insecticide, Fungicide, & Rodenticide Act: 1947, required testing & registration of the active ingredients of pesticides. 1988 version targeted older pesticides and new for ED50 and LD50 testing.
