Transcript ch. 22-pesticides - OCPS TeacherPress

 What

is a Pesticide?
Major Kinds of Pesticides
 Benefits
and Problems With Pesticides
 Alternatives to Pesticides
 Laws Controlling Pesticides Use
 Types:




Insecticides
Herbicides
Fungicides
Rodenticides
 Regulated
by the EPA
 Broad


spectrum pesticide
kills a variety of organisms, not just the targeted
organisms
Doesn’t degrade = doesn’t decompose = persist and
then accumulate in environment or organism.
o
First generation pesticide
• Inorganic compounds
•
•
Lead and mercury
Botanicals- plant derived pesticides
•
Nicotine
 Second


generation pesticide
Synthetic poison
Ex: DDT
for mosquitoes
used to control
malaria
 Chlorinated

Organic compound containing Chlorine



Hydrocarbons
Ex: DDT
Persist (do not degrade)
**Rachel Carson – “Silent Spring” = problems w/
pesticides
 Organophosphates



Developed during WWII
HIGHLY toxic (bees/humans), but do not persist
Currently used in agriculture



EX: Malathion, diazinon
Neurotoxin, especially children
Carbamates

Not as toxic to mammals

Ex: household sprays/traps
RACHEL CARSON…
ENVIRONMENTAL
GODDESS
 How
are organophosphates different than
chlorinated hydrocarbons?
 Selective


Herbicides
Kill only certain types of plants
Can be classified to the type of plant they kill

Broad-leaf herbicides




Ex: 2,4-D (2,4 dichlorophenoxyacetic acid)
Ex: 2,4,5 –T (2,4,5, trichlorophenoxyacetic
acid)
Used with wheat, corn, rice (cereal grains =
grasses)
Grass herbicides
 Nonselective
– kill all vegetation
 When
would you use a broad-leaf herbicide?
A grass herbicide
 Sprayed
to kill vegetation – Agent White,
Blue, Orange
 Ecological damage – decades to repair –
destroyed mangroves (habitat for fish and
coast protection from erosion), forests
destroyed
 Human effects


Agent Orange = (combination of broad leaf
herbicides + dioxins)  birth defects, stillbirths,
cancer
Dioxin in breastmilk – Vietnamese = 1800 ppt, US
= 4 ppt
 Benefit

1. : Disease control
Fleas, lice and mosquitoes carry disease
•
Malaria- mosquito
born
•
•
•
2.7 million people
die each year
Few drugs
available, so focus
is on killing
mosquitoes
DDT
 Benefit


2. : Crop Protection
Pests eat and destroy 1/3 of
world’s crops
Farmers save $3 to $5 for
every $1 they invest in
pesticides
 Name
the 2 reasons why pesticides are used?
 Problem:
Evolution of Genetic Resistance
Pest populations are evolving resistance to pesticides
(right)
Pesticide Treadmill
 Cost of applying pesticide increases



Because they must be applied more frequently or in larger
doses
While their effectiveness decreases

Because of increased genetic resistance in pests
Resistance Management


Refuge of untreated plants: allows mating of treated/untreated
pests to delay resistance
Remove surviving weeds after herbicide application
 Problem:


Kills non-target organisms
Spraying to kill insects can kill birds, fish, bees
Despite 33-fold increase in pesticides since the 1940s,
crop loss has not really changed
 Problem:

Creation of New Pests
Pesticide kills predator or competitor of minor pest
 Problem:
Persistence, Bioaccumulation, and
Biological Magnification

Bioaccumulation


The buildup of a persistent pesticide or
other toxic substance in an organisms body
Biological magnification
• Increased concentration
of toxic chemicals in tissues of
organisms at higher trophic
levels, stored in fat
• Ex: Peregrine falcons (right),
•
Bald Eagles
 Problem:


Mobility in the Environment
Do not stay where they are applied  harm non-target
organisms.
Move through soil, water (run-off) and air
 Effects

of Pesticides
Handling food with pesticide residue
•
•
Mild case:
nausea,
vomiting,
headaches
Severe case:
damage to
nervous system
(neurotoxin!!!)
 Long-term





Effects of Pesticides:
Cancer- lymphoma and breast
Sterility
Miscarriage
Birth defects
Harms immune system
 1984
Bhopal, India
 Explosion at pesticide plant released toxic
gas (cyanide)
 Many died immediately
 Others: problems to respiratory,
reproductive, nervous systems
 Using


cultivation methods to control pests
Interplant mixtures of plants (alternating rows):
polyculture !!
Crop rotation
 Biological


Control
Use of naturally occurring disease organisms, parasites
or predators to control pests
Must take care that introduced agent does not attack
unintended hosts
CANE TOADS
 Pheromones

and Hormones
Can use pheromones to lure pests to traps
 Reproductive


Controls
Sterilizing some of the members
Sterile male technique: sterilize in lab and then release
 IPM



Combination of pest control
methods that keeps pest
population low without
economic loss
Controls pests, not eradicate
Cons: requires a lot of
knowledge
 Conventional
pesticides are
used sparingly when other
methods fail
HOW DOES IPM DIFFER FROM
ORGANIC FARMING?
 Farmers
MONITOR pests and act when injury
threshold is reached.
 EX: Cotton – 1% of land; 50% of pesticide use
in US. – WOW!! Organic cotton helps reduce
pesticide use.
 Rice

Production in Indonesia
Predators of pests normally kept in check by
pesticides
IPM
Introduced
 Food,
Drug, and Cosmetics Act (1938) –FDCA –
determined pesticides need regulation!
 Delaney
Clause (1958) – no cancer causing
substances; not cover raw foods.
 Federal
Insecticide, Fungicide, and Rodenticide
Act (1947) – FIFRA – regulates what pesticides
are sold based on safety.
 Food
Quality Protection Act (1996) – stricter
guidelines on pesticide limits, covers raw food,
reduce time to ban harmful pesticide.
 Some
US companies still make banned or
seriously restricted pesticides

Product is exported
 Importation
of food tainted with banned
pesticides from other countries
 Global ban of persistent organic pollutants

Stockholm Convention on Persistent Organic
Pollutants (2004) – requires countries to
eliminate usage of the 12 most toxic chemicals.