CH 23: pesticides
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. What would you like to do?
The dilemma is:
whether to use them, or not use them!
• Pesticides have saved millions of lives by:
1. They kill insects and other organisms that carrydisease.2. Your book says they have increased the amountof food we grow – not all researchers agree onthis point.
pesticides have caused:
1. huge environmental problemsa. broad spectrum pesticides kill both pests andbeneficial organismsb. as they accumulate in the food chain.2. human health problemsa. for those that work with pesticides.b. pesticide poisonings and cancer.c. consumers worry about pesticides on food.• It appears in many cases that the harmful effects mayoutweigh the benefits.
any organism that interferes with human welfare
toxic chemicals used to control kill pests
toxic chemicals designed to kill insects
toxic chemicals used to kill plants
toxic chemicals used to kill fungi
toxic chemicals used to kill rodents
The perfect pesticide does not exist yet.• If it did, it would have the following characteristics.
1. Narrow spectrum – that is, it would kill the pest only and notharm other organisms2. Biodegradable – it would only last a short time in theenvironment and then degrade3. It would stay put in the environment and not spread to other areasor ecosystems
Most pesticides are ____ that kill many speciesin addition to the pest• The species killed may include beneficial species such as importantpollinators of plants.
broad spectrum pesticides
The first generation of pesticides include:
- 1. Inorganic compounds (lead, mercury, arsenic)2. Botanicals – natural plant chemicals used as pesticides and highly toxic toinsects aquatic life and bees (very important pollinators). One advantageis botanicals are quickly and easily broken down by microorganisms so donot persist in the environment.a. nicotine from tobaccob. pyrethrin from chrysanthemum flowersc. rotenone from roots of the derris plant
- 4. Synthetic botanicals – man-made pesticides modified from naturalbotanicals.• Ex. pyrethroids from the pyrethrin of chrysanthemum flowers.• Pyrethroids are non-persistent, slightly toxic to mammals and bees, buttoxic to fish.• Resistance to pyrethroids is occurring at an astounding rate.
The first generation pesticides include:
- 1.inorganic compounds (lead mercury arsenic)
- 2. botanicals
- 4. synthetic botanicals
man madesynthetic poisons in use today
• 20,000 pesticide products withcombinations of 675 active chemicalingredients
the first of the 2nd generationpesticides (1939)
• DDT was cheap and effective against mostpests• DDT saved millions of people from deathfrom Malaria and Yellow Fever and wasrevered as a “miracle” chemical• It was hoped it would eradicate all pestsonce and for all.• 1939 – DDT produced• 1945 – 12 species resistant to DDT
• See sharp decline in predatory birds (brownpelican, peregrine falcon, eagles)• DDT prevents the uptake of calcium in the dietleading to the thinning of eggshells in birds.• 1973 – DDT banned for use in U.S. except foremergency use.• Still produced in U.S. and sold to othercountries.• DDT comes back in products we import.• 1976 – >200 species resistant• 1980 - >450 species resistant
(includes DDT) = organic compoundswith chlorine• generally broad spectrum, most slow to degrade (persistent)• widely used from 1940 – 1960• many have been restricted or banned• especially since publication of Silent Spring (1963) by RachelCarson
1. Chlorinated hydrocarbons
(includes malathion) = organic compounds withphosphorus• developed during WWII with development of nerve gas• organophosphates are more poisonous than other types ofinsecticides• highly toxic birds, mammals, bees, aquatic organisms• they are not as persistent as chlorinated hydrocarbons and havereplaced them in agriculture to a large extent.
(include carbaryl and aldicarb)• derived from carbamic acid• not as toxic to mammals as organophosphates• still is broad spectrum poison
kill onlycertain kinds of plants
kill allvegetation (agent white, blue, orange)used to destroy crops and exposehiding places during Vietnam war
toxins formed during themaking of herbicides– dioxins can cause birth defects
The benefits of pesticides
1. prevent diseases transmitted by insects2. reduce crop losses to increase agricultural productivity3. reduce competition between crop plants and weeds4. reduce plant diseases caused by plant pathogens such asfungi and bacteria5. human disease control
Problems with pesticide use
- 1. Genetic resistance – an inheritedcharacteristic that reduces theeffect of pesticide on a pest2. Decreased effectiveness – overtime pesticide does not work aswell3. Ecosystem imbalance –pesticides effect unintendedtargets such as importantpollinators and natural predators of the pest
- 4. Creation of new pest – pesticides mayinadvertently kill an important insectpredator allowing a species who’spopulation was naturally controlled, togrow out of control5. Persistence in environment – somepesticides may take years to breakdown and become less toxic6. Bioaccumulation – pesticideconcentrations may buildup within anorganism over time.
- 7. Biological magnification –increased levels of pesticideconcentration as you go tohigher trophic levels of the foodweb8. Mobility in the environment –pesticides don’t stay where theyare applied9. Short and long term risks tohuman health – pesticidespoison 67,000 people per yearin U.S.
– is the growing of one species of plant over anexpansive area.
- • Most monocultures represent a huge food source for insect pestsand contain few natural predators to control pest species.
since the effectiveness of pesticidesdiminishes over time, the cost of applying pesticides increasesas they have to be applied more frequently or in higher doses.
Risks of Pesticides to Human Health
- • Short Term Effects of Pesticides
- – Mild exposure
- • Nausea
- • Vomiting• Headaches
- – Higher exposure levels
- • Permanent damage to nervous system and other organs
- • Death
Long term effects of pesticides
- – Leukemia
- – Cancer of Lymphatic System,Brain, Lungs, Testicles, Breasts
- – Sterility
- – Birth Defects (particularlystunted limbs)
- – Compromised Immune System
- – May increase risk of Parkinson’sdisease (shaky palsy), atremoring of the limbs
Pesticides lead to ___.
problems in animals
• Pesticides and Children
• Poisoning – children more susceptibledue to activity on floor• May effect development of intelligenceand motor skills
ALTERNATIVES TO PESTICIDES
• Alternative ways to control pests, includingcultivation methods, biological controls,pheromones and hormones, reproductivecontrols, genetic controls, quarantine,integrated pest management, and irradiatingfoods.
Proper ____ to produce morevigorous plants
plant cultivation methods
the use naturally occurringorganisms to keep populations in check. Using predatorsand disease to control population numbers. Naturalparasites, disease, predators
(sexual attractants) chemicalmessengers used to attract and trap insects or effect theirdevelopmen
manyfemales mate only once with non-fertile male so do notproduce young.
Reproductive controls - sterile male technique
producing crops that are geneticallyresistant to disease or insects
combination ofag methods that employs biological control, pheromonetraps, cultivation methods, resistant crops varieties, andsmall amounts of pesticide.
Integrated pest management (IPM)
restricting movementof materials that may contain pests
quick heat that killspests but does not hurt plant
quick freeze that killspests but does not harm crop
after harvest, food isexposed to radiation and pests arecontrolled
Three U.S. laws that regulate pesticides:
the Food, Drug, andCosmetics Act1; the Federal Insecticide, Fungicide, andRodenticide Act2; and the Food Quality Protection Act3.
• These laws have been modified over time to:
1. regulate pesticides in food12. establish acceptable/unacceptable levels of pesticides in foods1(Miller Amendment)3. insure no substance shown to cause cancer in lab animals ispermitted in processed food1 (Delaney Clause)4. require testing and registration of active ingredients ofpesticides25. establish pesticide residue limits that pose negligible risk inprocessed and raw foods3
THE MANUFACTURE AND USE OFBANNED PESTICIDES
• Some U.S. companies continue tomanufacture pesticides that are bannedfor use or heavily restricted in the U.S.• They sell them to foreign countries andthe toxins come back to us in the foods weimport from those countries.
andthe purpose of the StockholmConvention on Persistent OrganicPollutants
Persistent organic pollutant
a group of persistent,toxic chemicals thatbioaccumulate in organisms andcan travel thousands of milesthrough air and water tocontaminate areas far away fromtheir source.
Persistent organic pollutant(POP) –
• The Stockholm Conventionserves to protect humanhealth and the environmentform the 12 most toxic
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