Chapter 20 Pesticides and Pest Control
20.1 Pesticides: Types and Uses
A. Pest – any species that competes with us for food, invades lawns and gardens, destroys wood in houses, spreads disease or is simply a nuisance
B. Pesticides – chemicals to kill organisms or biocides
1. Insecticides – insect killers
2. Herbicides – weed killers
3. Fungicides – fungus killers
4. Nematocides – round worm killers
5. Rodenticides – rat and mouse killers
C. Been in practice by competing species forever
D. Plant defenses, natural selection – co-evolution
E. First generation of pesticides: generally weapons borrowed from plants
1. 500 B.C. Sulfur
2. 1400’s toxic compounds of heavy metals (arsenic, lead, mercury) used until 1920’s
3. 1600’s – nicotine sulfate from tobacco
4. 1800’2 pyrethrum from heads of chrysanthmums and rotenone form the root of the derris plant
F. Second generation
1. Began in 1939 with DDT – synthetic organic chemicals
2. One pound for each person on the earth is used each year of organic pesticides.
3. Cultivation of corn, cotton, wheat and soybeans uses 70% of all insecticides and 80% of all herbicides.
4. Also added to products from carpets to contact lenses
5. Broad spectrum – kills a wide variety of pest
6. Vary in persistence (how long in environment)
7. Most organophosphates are neurotoxins and can also work on all other animals including humans
20.2 The Case for Pesticides
A. Save lives
B. Increase food supplies and lower food costs
C. Increase profit for farmers
D. Work faster than alternatives
E. Health risks of pesticies are insignificant compared with health benefits and other benefits
F. Presently – safer and more effective pesticides are being developed – require very low doses
G. Search continues for ideal pesticide
1. kill only target pest
2. harm no other species
3. disappear or break down into something harmless after doing it’s job.
4. Not cause genetic resistence
5. Be cheaper than doing nothing
20.3 The Case against Pesticides
A. Build Genetic Resistance
1. Insects can develop immunity through natural selection to pesticides in less than 5-10 years – faster in tropical areas
B. Kill natural predators
1. kill wasps, spiders and predatory beetles, makes way for more pests
2. also could cause explosions of alternate pests that naturally would have been kept in check
C. Causes the pesticide treadmill – farmers pay more for a pesticide treatment that becomes less and less effective
1. pesticide use is up 33% yet, food loss to pest is 6% higher than in 1940’s
2. 50% cut in pesticide use would only cause a .2%price rise but raise the average income for farmers 9%
D. Pesticides don’t stay put
1. wash off
2. get on off target areas – air application
3. harm wildlife – biomagnification and bioaccumulation
E. Human health problems
1. Farm workers especially susceptible to pesitcide poisonings
2. Pesticides in water runoff problems for all people
3. Pesticides in the house – problem
4. Children more susceptible
5. Pesticide persistance rated as #3 environmental health hazard by EPA
6. Pesticides linked to cancer
a. children in homes where lawn sprayed 4 times more likely to suffer from cancers of muscle or connective tissue
b. Children whose homes had no pest strips – 3 times more likely to develop lukemia
7. Problems with manufacture – Bhophal, India
a. Dec. 2, 1984 – Union Carbide pesiticide plant – 40 tons of Methyl isocyanate gas leaked and caused an explosion – escaped gas killed over 5,000 people – 20,000 had serious injuries blindness and lung damage. Union Carbide claimed it was sabotage, was sued and paid $4.1 billion in damages.
20.4 Pesticide regulation in US
A. FIFRA – Federal Insecticide, fungicide and rodenticide act – all pesticides must be approved by EPA for general or restricted use
B. Tolerance level – amt of toxic residue that can legally remain on crop when the consumer eats it
C. Reference dose – how much is safe for consumer to eat. Recommended 10 times less for children
D. Recently test of pesticides on wildlife not required
E. Many banned chemicals in US are sold to developing countries and used on crops – then imported to US –circle of poison – also problem with NAFTA
F. Inert ingredients not tested – secrets due to patents may have estrogenic or endocrine effects
G. Laws poorly enforced
H. Until 1990 – EPA had to compensate companies whose pesticides were pulled – now cost goes to manufacturers
I. Cumulative pesticides effects
20.5 Solutions: other ways to control pests
A. Natural Chemicals
1. Ants – cayenne pepper, boric acid, vinegar
2. Mosquitioes – plant basil, vinegar, basil oil, lime juice
3. Cockroaches – boric acid, bay leaves, banana spiders, trap grease inner neck of bottle and put in food scraps
4. Fleas – dips of oils from natural plants – green light traps – diatomaceous earth
5. Lawn weeds – raise lawn mower blade to 3-4in so grasses grow strong root base and hinder weed growth, pull weeds and dose the hole with soap solution or urine
6. Garden – hose down with soap solution
B. Cultivation practices
1, crop rotation
2. planting times altered to beat pest – plowing at night reduces 50-60% of weeds
3. Trap crops
4. Intercropping, agroforestry
C. Genetically resistant plants and crops
D. Natural Enemies – Biological control
1. Wasp – Paraguay wasp – saved African cassava, lady bugs
2. Slower, more difficult to apply and killed by neighbors using pesticides
3. Need to be concerned not to introduce exotics too fast
E. Biopesticides
1. plant poisons to kill insects – neem tree seeds
2. Microbes – Bacillus thuringensis (Bt) toxin
F. Insect Birth control
1. Male sterilization – elimenated screw worm in SE US
2. Phermones – chemicals that attract other insects –bait a field – attract them and then treat the concentrated area with pesticides – kill more with little amount of pesticide
3. Use insect hormones to keep insects juvenilles – ex. Fleas
4. Problem – sometimes timing crucial, and costly to produce
G. Hot water
1. Boiling water sprayed on plants and kill weeds and insects
2. Works on cotton, alfalfa and potatoes and oranges in FL
H. Radiation
1. low doses of radiation kill pest on food
2. not much research
3. some opposition - makes food look healthier
4. major problem – worker exposure and waste products
I. Integrated pest management (IPM)
1. a mix of cultivation and biological, chemical methods applied at the right time
2. goal to reduce crop damage, not eradicate all pests
3. Many countries using this now – expensive to start
4. US is encouraging IPM by: