Chapter 13. Pest – any organism that is harmful or destructive or interferes with humans or our...
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Transcript of Chapter 13. Pest – any organism that is harmful or destructive or interferes with humans or our...
Chapter 13
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
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.
Pesticides Insecticides – insects killers Herbicides – weed killers Fungicides – fungus killers Rodenticides – rat and mouse killers
Herbivores overcome plant defenses through natural selection; coevolution
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 -
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
Compound Class Examples Persistence in the Environment
Organochlorides (chlorinated hydrocarbons)
DDT, DDD, aldrin, chlordane, toxaphene, lindane
High - 5 to 15 years
Organophosphates diazinon, malathion, parathion, chloropyrifos
Intermediate - 1 week to several weeks
Carbomates Carbaryl (sevin), matacil, temik, zectran, aminocarb
Low- 2 weeks or less
Pyrethroids decamethrin, permethrin, bifenthrin
Low- days
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
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
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.
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.
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..???
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 pyramid Chemicals such as
pesticides tend to increase their concentration by approximately ten times as they move upward through the trophic levels.
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
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
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
1955 - Dieldrin sprayed to control mosquitoes
Malaria was controlled
Dieldrin didn’t leave the food chain
Domino effect of the spraying
Happy ending
U.S. federal agencies EPA USDA FDA
Tolerance – the limit to the amount of pesticide that can remain on food.
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
pre-existing 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
FQPA – the Food Quality Protection Act of 1996 Set standards for pesticides applied to foods
(with a special concern for children). Requires that
1. pesticide be prohibited from being used if linked to cancer.
2. all possible exposure to pesticide be evaluated.3. older pesticides be reevaluated to see if they
meet new standards.4. standards apply to both processed and raw
foods.
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
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
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 (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
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
1.Biological control - using natural enemies, or predator bugs, to control pests.
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.2.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.3.Genetic control - breeding plant varieties that are resistant to pests.
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.
4.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.
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.