Chapter 13

Pest – any organism that is harmful or destructive or interferes with humans or our social or economic endeavors.

Natural pest control — predators, parasites, disease organisms. In natural ecosystems In many polycultures Agro-ecosystems

Economic threshold – measure used to determine when damage caused by pest outweighs cost of applying pesticide.

Insurance spraying – prevention

Cosmetic spraying – used to keep fruits and vegetables looking desirable to consumers.

Pesticides Insecticides – insects killers Herbicides – weed killers Fungicides – fungus killers Rodenticides – rat and mouse killers

Herbivores overcome plant defenses through natural selection; coevolution

First-generation pesticides - natural chemicals from plants

Second-generation pesticides – synthetic chemicals produced in laboratories. Paul Muller - discovered DDT would work as

potent insecticide in 1939; awarded Nobel Prize in 1948

Broad-spectrum agents – toxic to many pests and non-pest species. Chlorinated hydrocarbons – DDT Organophosphates - malathion, parathion

Selective or narrow spectrum agents -

Persistence – length of time (usually years) they remain deadly in the environment and, biologically magnified in food webs

Non-persistent pesticides – break down into simple nontoxic substances within a few weeks; very toxic and pose serious danger to humans.

LD50 – the amount of a chemical, given all at once, which causes the death of 50% of a group of test animals.- way to measure acute toxicity of the chemical.- LD stands for lethal dose.

Insecticide Examples

Compound Class Examples Persistence in the Environment

Organochlorides (chlorinated hydrocarbons)

DDT, DDD, aldrin, chlordane, toxaphene, lindane

High - 5 to 15 years

Organophosphates diazinon, malathion, parathion, chloropyrifos

Intermediate - 1 week to several weeks

Carbomates Carbaryl (sevin), matacil, temik, zectran, aminocarb

Low- 2 weeks or less

Pyrethroids decamethrin, permethrin, bifenthrin

Low- days

Compound Class Examples

Triazines Atrazine, cyanizine. simazine

Dinitroaniline oryzalin, triflualin

Phenoxy 2,4-D; 2,4,5-T; MCPB

Thiocarbamate butylate, cycloate, EPTC

Acidamine alachlor, propachlor

Biologist - noticed DDT use was increasing; mainly to control mosquitoes

Silent Spring - 1962 Voiced potential

threats of uncontrolled use of pesticides; especially effects of biomagnification.

Gave impetus to the US environmental movement

Discovered in 1930s; killed various kinds of insects.

Used primarily 1940s – 1960s (WWII); to control spread of body lice on

soldiers. Used in tropics to stop spread of malaria. By controlling pests, increased crop yields. Banned in US (1972) but still produced in

the US. Used by many countries that export

produce to the US; presence of DDT in our body tissues.

Pests became resistant; larger amounts have to be used to get same effect. Pesticide treadmill – use of stronger and

more frequent doses to be effective. Accelerate the development of resistance –

5 to 10 years sooner in the tropics.

Once pests became resistant, their populations exploded.

Pesticides often kill or harm non-target organisms – Kill natural predators and parasites that help

control pests

Predatory birds – egg shells cracked, dead chicks, lower reproductive rates.

“Vanishing of the Bees”; colony collapse..???

Bioaccumulation – process of accumulating higher and higher doses up the trophic levels of the food chain.

Biomagnification – the multiplying effect of bioaccumulation in a food chain.

A substance biomagnifies when It is long-lived Producers make it more concentrated It is fat-soluble

Biomagnification pyramid Chemicals such as

pesticides tend to increase their concentration by approximately ten times as they move upward through the trophic levels.

Only 0.1 - 2% of the pesticide applied by aerial or ground

spraying reaches the target pest. Rest pollutes air, water,

harm wild life, affect human health

Persistence in nature; magnification in food chain

Links to cancer, birth defects, infertility

Expensive for farmers

Some insecticides kill natural predators and parasites that

help control the pest population

Pollution in the environment

Some harm wildlife

Some are human health hazards

David Pimentel: Pesticide use has not reduced U.S. crop loss to pests Loss of crops is about 31%, even with 33-

fold increase in pesticide use High environmental, health, and social

costs with use - $5-10 in damages for every $1 spent

Use alternative pest management practices could halve the use of chemical pesticides on 40 major US crops

Campbell’s soup tomatoes in Mexico, Rice in Indonesia, Sweden

Pesticides industry refutes these findings

Best-selling herbicide (Roundup), Monsanto

Advantages – does not harm living things, degrades into harmless substances within weeks

Disadvantages - resistant weeds , expensive to develop other pesticides

1955 - Dieldrin sprayed to control mosquitoes

Malaria was controlled

Dieldrin didn’t leave the food chain

Domino effect of the spraying

Happy ending

U.S. federal agencies EPA USDA FDA

Tolerance – the limit to the amount of pesticide that can remain on food.

FIFRA – the Federal Insecticide, Fungicide, and Rodenticide Act of 1972 Requires manufacturers to register pesticides with the

EPA before marketing them and to test toxicity levels Required the reevaluation of 600 active ingredients in

pre-existing pesticides Allows the EPA to regulate the amount of pesticide

residue on food Says EPA will consider public’s overall exposure when

making decisions to set standards Allows EPA to leave inadequately tested pesticides on

market; does NOT require immediate removal from market.

Allows EPA to license new chemicals without full health and safety data

FQPA – the Food Quality Protection Act of 1996 Set standards for pesticides applied to foods

(with a special concern for children). Requires that

1. pesticide be prohibited from being used if linked to cancer.

2. all possible exposure to pesticide be evaluated.3. older pesticides be reevaluated to see if they

meet new standards.4. standards apply to both processed and raw

foods.

Effects of active and inactive pesticide ingredients are poorly documented

Circle of poison/boomerang effect – residues of banned chemicals exported to other countries may come back on food; winds carry persistent pesticides such as DDT

US citizens contain some pesticide residue in their body tissue from pesticides that have been banned for decades

1998 – 50 countries developed treaty that requires exporting countries to have consent from importing countries for exports of 22 pesticides , 5 industrial chemicals

2000 – 100 countries signed to phase out 12 of the most hazardous persistent organic pollutants (POP’s), 9 of them hydrocarbons (DDT)

United States has not signed this agreement

We can sharply cut pesticide use without decreasing crop yields by using a mix of cultivation techniques, biological pest controls, and small amounts of selected chemical pesticides as a last resort.

IPM

Integrated pest management (IPM) Coordinate cultivation,

biological controls, and small amounts of selected chemical pesticides to reduce crop damage to an economically tolerable level.

Disadvantages Expert knowledge What works in one area

may not work elsewhere

Fool the pest : rotate crops, adjust plant times

Implant genetic resistance - GMO’s; genetic control

Bring in natural enemies; natural predators (biological control)

Use hormones/insect perfumes (pheromones)

Genetic controls Cultural control

1.Biological control - using natural enemies, or predator bugs, to control pests.

For example, ladybugs can be purchased at most garden stores to help control aphids, a common garden pest.

Must be careful – controls may also attack beneficial species.2.Pheromones - chemicals that a species emits to attract members of the same species. Scientists use these pheromones to trap pests in devices baited with poison.3.Genetic control - breeding plant varieties that are resistant to pests.

For example, plants can be bred to produce chemical barriers that kill or repulse pests.

Another example is to release a group of sterilized males into the environment. These sterilized males mate with females, which prevents future attempts for the female to mate.

4.Cultural control - where the environment is altered in such a manner that pests cannot thrive.

Changing bed linens to prevent bedbugs or cleaning the house to prevent roaches are examples.

Organic foods - grown with little or no pesticides, chemical fertilizers, antibiotics, or hormones.

BUT, according to United States Department of Agriculture – must use organic fertilizer and pheromones to disrupt insect mating cycle.

Organic farming produces smaller yields than nonorganic farming methods.

However, sales of organic foods have increased by 20% each year for the past 10 years.