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9.3 Pest Control
Look,
Earl! No
more
pests!
Pests damage crops
Stats:
–
–
–
NA – 10% crop damage
Kenya – 75% crop damage
World wide – 1/3
Pest – any org that occurs where you don’t want
it or in large enough numbers to cause
damage.
cotton stainer - minor
pest of cotton in the
southern Florida
barley, corn, millet, oats,
rice, rye, sorghum,
sugarcane, timothy, and
wheat may be consumed,
as well as wild or weed
grasses.
Adult armyworm
larva of the armyworm, Pseudaletia unipuncta
Why problem for crops?
B/c easy to find & damage
Pesticides – substance that kills
pests
Ex: Aldrin, DDT, Lindane, Malathion, Carbaryl
Insecticides – kill insects
Drawbacks of Pesticides
Health concerns
–
–
Cancer
Chemical leaks
Carlitos, child of
farmworkers,
born with birth
defects
attributable to
pesticides (PBP).
Source:
Sarasota/Manat
ee Farmworker
Supporters
A train derailment near Milligan, Florida. The train carried
chemicals, which were spilled at the site.
(©Bettmann/Corbis. Reproduced by permission.)
Pollution & Persistence
–
•
•
•
•
Persistent pesticides – don’t break down fast
into harmless chem – accumulate in soil & H2O
• DDT – 1940s to kill mosq. & lice (malaria &
typhus)
Water – fish – birds – thin shells
Penguins, pelicans, peregrines, eagles
Banned
In US, 60 diff pesticides found in ground
water
Penguins,
pelicans,
peregrines,
eagles
Resistance
ability to tolerate a particular chemical. It
evolves through natural selection
• 500 species have developed res. Since 1940s
Biological Pest Control – using living
orgs or naturally produced chem. to
control pests.
•
•
•
resistance takes longer to evolve
usually don’t harm orgs other than
pests
Predators & Pathogens
–
•
pathogen – org that causes disease.
These are sometimes used against pests.
Ex: Bacillus thuringensis – bacteria
that kills insect larvae
A range of products to keep
unwanted visitors out of
your garden and buildings.
Predators & Pathogens
Pathogen – org that causes disease. These are
sometimes used against pests.
• Ex: Bacillus thuringensis – bacteria that kills insect
larvae
Chemicals from plants
Extracts from plants used against pests
• Ex: chrysanthemum
Disrupting Insect Breeding
Pheromones – chemicals produced by one org that affect the
behavior of another.
•
Farmers spray to interfere w/ mating
•
Reduce numbers better than pesticides
•
Expensive to make so not widely used
Treat males w/ x-rays – can’t reproduce