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71 terms

Pesticides

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Pesticide
a pesticide that kills a variety of organisms, not just the targeted organisms
to kill pests
All insecticides are pesticides but
but not all pesticides are insecticides
fungus pesticide
fungicide
mice/rat pesticide
rodenticide
plant/weed pesticide
herbicide
"Silent Spring"
by Rachel Carson
about contamination of environment-insecticides that would kill all the birds
brought about awareness of environmental issues (mainly about DDT)
2 kinds of insecticides
natural (botanicals) & synthetic
examples of natural insecticides
nicotine, pyrethrine (extract of a mum flower that paralyzes insect), rotenone (legune from India)
Types of synthetic insecticides
1. Organochlorine (chlorinated hydrocarbons)
2. organophosphorus
3. Carbamates
What gives the synthetic insecticide it's toxicity
the element i.e. chlorine, phosphorus, nitrogen...
1st generation pesticide
inorganic compounds and botanicals i.e. lead, mercury, nicotine and pyrethrine
2nd generation pesticide
synthetic poison i.e. DDT
Major Benefit of Pesticides
Crop Protection
oests eat and destroy 1/3 of world's crops
farmers save $3-$5 for every $1 they invest in pesticides
Chlorinated Hydrocarbons
high environmental resistance
low mammalian toxicity
fat soluble
biomagnifies
DDT is what kind of synthetic pesticide?
chlorinated hydrocarbons
The "Dirty Dozen" are what kind of pesticides?
organochlorine
Endrin
organochlorine manufactured in STL
part of the Dirty Dozen
Mirex
used to control fire ants
part of the Dirty Dozen
Reasons why we don't use organochlorine
1. Persistent in the environment
2. Fat soluble (concentrate in fat tissue of organisms-bioaccumulates and biomagnifies)
3. Universal poison (kills both good and bad insects)
bioaccumulation
accumulation of toxic substancewithin an organism
can cause biomagnification
biomagnification
accumulates more concentration as it moves up the food chain
i.e. peregrine falcons
Relationship between organochlorines and birds
organochlorine upsets the estrogen cycle of female birds and they have thin eggs shells that make them break easily
especially found in predator birds
Genetic resistance to insecticides (DDT)
prey have greatest reproductive capability, therefore they are more probable to have genetic resistance
predator gets a double dose from environment
prey is most likely to be genetically resistance
Number of species resistant to DDT in 1945
12
Number of species resistant to DDT in 1960
137 (65 ate our crops)
Number of species resistant to DDT in 1980
over 200
Number of species resistant to DDT in 2000
less than 100
DDT was banned in...
1973
Organophosphates
low environmental resistance
high mammalian toxicity
water soluble
doesnt biomagnify
What is the most poisonous insecticide for humans?
organophosphates
Why was organophosphates developed?
developed in WWII by American gov't as an agent for chemical warfare (nerve gas)
Sarin
organophosphorus gas used in Tokyo subway
given to Sudam Hussian by US
Parathion
organophosphorus liquid that is highly toxic
Malathion
organophosphorus substance sprayed over Dallas (1970) because of an outbreak of insefilitus that was carried by mosquitos
What is the least toxic of organophosphates
Malathion
Pros of organophosphates
effective
doesnt persist in environment
doesn't biomagnify
Cons of organophosphates
very toxic
Effects of organophosphates on humans
upsets message from nerve to brain
nervous twitching/uncontrollable nerve movements
caused dilated pupils
Carbamates are derived from
methyl isocyanate (MIC)
organic compounds that contain nitrogen
What is the newest class of synthetic insecticides?
Carbamates
Active chemicals in carbamates
nitrogen and carbon (CN)
Cyanide
carbamate used to use people on death row in TX
Most well-known carbamate
sevin (used on pets-low mammalian toxicity)
Carbamates
low->medium environmental resistance
medium mammalian toxicity
water soluble
very little to no biomagnification
Pesticide treadmill
cost of applying pesticide increases because they must be applied more frequently or in larger doses
effectiveness decreases because of increase in genetic resistance in pests
Resistance management
strategies for managing genetic resistance in order to maximize the period in which a pesticide is useful
delays the evolution of genetic resistance-refuge of untreated plants
Problems with Pesticides
Persistence, Bioaccumulation, Biomagnification, Mobility-do not stay where they are applied, move through soil, water, air
Short-term effects of Pesticides
handling food with pesticide residue
mild case: nausea, vomiting, headaches
severe case: damage to nervous system
Long term effects of Pesticides
cancer-lymphoma
breast cancer
sterility
miscarriage
birth defects
reduce immunity
potential connection to Parkinson's disease
**Synergism
the sum of pesticides produces an enhanced effect
i.e. mercury + heat=enhanced toxicity
**Antagonism
sum of pesticides produces a reduced effect
i.e. tetroculin (acne meds) can't be taken with dairy products because it reduces its affectiveness
Alternatives to Pesticides
1. Cultural Methods
2. Biological Control
3. Pheromones
4. Hormones
5. Reproductive Controls
Cultural Methods to control Pesticides
cultivating a crop to minimize insect attacks
plant crop in alternate years so insects can't build up in that area
interplant mixtures of plants (altering rows)
proper timing of planting, fertilizing, and irrigating
crop rotating
Biological control to control Pesticides
use of naturally occurring disease organisms, parasites or predators to control pests
must take care that introduced agent does not attack unintended hosts
i.e. parasites, lady bugs
i.e. using bacteria and viruses that only attack the insect eating the crops
Phermones to control Pesticides
sex attractant/insect attractants
used to lure pests to traps
Hormones
causes changes in organism
causes insect metamorphosis change
if applied at the wrong time in life cycle, insects can be killed off
Reproductive controls to control Pesticides
sterilization controls
i.e. sterilize male screw worm so it cannot reproduce and lay eggs on deer's open wounds
when screw worm was eradicated, the deer population went up
IPM
Integrated Pest Management
combination of pest control methods that keep pest population low without economic loss
conventional pesticides are used sparingly when other methods fail
uses the judicious use of pesticides
Manufacture and Use of Banned Pesticides
some US companies still make banned or seriously restricted pesticides (produce is exported)
may lead to the importation of food tainted with banned pesticides
global ban of persistent organic pollutants (POP's) Stockholm Convention of Persistent Organic Pollutants
Selective herbicides
kill only certain types of plants
can be classified to the type of plant they kill
-broad-leaf herbicides
-grass herbicides
i.e. 2,4-D; 2,4,5-T; Agent Orange
2,4-D
weed herbicide
2,4,5-T
herbicide for trees
Hochimen Trail
trail was covered with trees and virus
US went and sprayed with 2,4,5-T to kill trees and added 2,4_D to kill vines
-made 50/50 mixture called "Agent Orange"
Agent Orange
used to spray Hochimen Trial
effect on troops: cancer (carcinogenic), birth defects (teratogenic), genetic defects (mutagenic)
What caused harmful effects from Agent Orange?
contaminent in 2,4,5-T: Dioxin (TCDD)
TCDD
Dioxin; contaminant in Agent Orange
PCB
Polychlorinated Biphenyls
used in electrical transformers-now banned
have same environmental effect at DDT
PBB
PolyBrominated Byphenyls
flame retardent
used in baby clothing and baby blankets
MIC
methyl isocyanate
What is the building block of all carbamate insecticides?
MIC
Bhopal, India
1984; gives off cyanide has if mixed with water
killed 5,000 people