Pests and Pesticides

PROS

Kill unwanted pests that
carry disease (rats,
mosquitoes, Tse-Tse
flies)

Increase food supplies

More food means food
is less expensive

Reduces labor costs on
farms

Food looks better

CONS

Resistance creates
pesticide treadmill (i.e.
Roundup)

Pesticide runoff 🡪 water
contamination i.e.
Atrazine

May kill non-target
species. i.e. bees

Bioaccumulation/
biomaginification, i.e.
DDT

Chemical Pesticides

DDT

Used to control mosquito populations and mosquito transmitted
diseases like malaria, west nile, and dengue fever

Chlorinated hydrocarbon – neurotoxin that is persistent and
biomagnifies

Causes weak egg shells in predatory birds like the bald eagle and
California condor,

Malathion (mosquitoes), parathion (cotton)

Organophosphates – neurotoxin (chemical weapon)

Not persistent, no biomagnification or water contamination, but highly
toxic to a variety of non-target species (including humans)

Atrazine

Herbicide used both before and during planting to kill weeds.

Persistent, likely an endocrine disruptor and possibly a carcinogen

Major concerns include toxicity to amphibians and concentrations in
the drinking water supply

Biological Control

Using natural predators to control pests

Examples:

Ladybugs eat aphids

Parasitic wasps eat boll weevils (cotton) and
gypsy moths (tree leaves)

Dragonflies eat mosquitoes

Pros – no chemicals, targeted pest control

Cons – could become an invasive specie

i.e. cane toad (brought in to eat cane beetle)

Endocrine Controls

Pheromones – sex attractants lure pests into
traps or attract natural predators

Hormones – disrupt insect life cycles preventing
reproduction

Sterilized insects – release sterilized insects to
reduce the yields of new insects

Pros – narrow, no genetic resistance, do not
harm non-target species

Cons – costly and time consuming to develop,
may take a long time to work.

Hormones have to be released at specific time to
work and may impact other species

Pesticide Treadmill

The result of many pests and weeds short
life cycles and ability to evolve quickly

A new pesticide is released and is very effective.

The effective pesticide is widely used, allowing the
pests to evolve resistance.

The pesticide now requires higher doses and more
frequent applications until eventually it may be
completely ineffective

Process repeats with another new pesticide

Alternatives to pesticides

IPM (see HW reading)

Polyculture, Intercropping, Planting
pest-repellent crops

Mulch to control weeds

Rotating crops to disrupt insect cycles

Natural insect predators – ladybugs, preying
mantis, birds

Using Pheromones to attract insects to traps

Releasing sterilized insects (insect birth control)

Endocrine disrupting chemicals

Laws

Federal Insecticide, Fungicide and Rodenticide Act
(FIFRA – 1947, 1972)

Regulates pesticide use in the US, requires EPA to test
active/inactive ingredients in pesticides

Testing usually falls on chemical companies to show ingredients
will not have adverse effects on environment/humans

Food Quality Protection Act (1996)

Protects the health of children by regulating the amount of
pesticide residue allowed to remain on food

Toxic Substances Control Act (TSCA – 1976)

Gives EPA the power to regulate chemicals (but NOT pesticides,
food or cosmetics)

Most existing chemicals were grandfathered in

Covers lead, asbestos, PCBs radon, CFCs and Dioxins

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