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Chapter 10

PESTS

&

PESTICIDES

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OUTLINE

• Pests

• Pesticides

Types

Benefits

Problems

Alternatives

Reducing Exposure

Regulating Use

• Organic Farming

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PESTS AND PESTICIDES

• BIOLOGICAL PESTS - organisms that reduce the availability, quality, or value of resources useful to humans (this varies among cultures)

(Dandelions are considered “weeds” here, but they are eaten and cultivated in other countries)

Only about 100 species of organisms cause 90% of crop damage worldwide.

- Insects are most frequent pests.

Insects account for 3/4 of ALL species

Pests tend to be generalists, r-selected strategists, pioneer organisms, and compete effectively against more specialized endemic species

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TYPES OF PESTICIDES

• PESTICIDE – a chemical that kills “pests”

- BIOCIDE - kills wide range of organisms

- HERBICIDE - kills plants

- INSECTICIDE - kills insects

- FUNGICIDE - kills fungi

- ACARICIDE - kills mites, ticks, and spiders

- NEMATICIDE - kills nematodes (roundworms)

- RODENTICIDE - kills rodents

- AVICIDE - kills birds

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EARLY PEST CONTROLS

• Sumerians (Mesopotamia) controlled insects

with sulfur 5,000 years ago.

• Chinese used mercury and arsenic to control

pests 2,500 years ago.

• Romans burned fields and rotated crops to

reduce crop disease.

• Many cultures have used spices, salt, smoke,

vinegar and alcohol to preserve foods

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CONVENTIONAL PESTICIDE USE

The US accounts for over 1/6th of the

World’s total usage of pesticides!

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DDT – Dichloro-diphenyl-trichloroethane

• Era of SYNTHETIC ORGANIC PESTICIDES

began in 1939 with DDT.

• Extensive use: Inexpensive, stable, easily

applied, highly effective, and long-lasting

• By 1960’s, evidence of concentration through

food chains. Carnivorous birds such as eagles

suffered egg shell thinning leading to an

inability to reproduce.

• Endocrine hormone-disrupting in top predators

(eagles, hawks, falcons, pelicans)

• Relatively non-toxic to mammals

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DDT

• DDT degrades in the environment into

DDE (Dichloro diphenyl dichloroethylene)

DDE is particularly dangerous because it is

fat-soluble like other organochlorines

Concentrations tend to increase throughout

life. The major exception is the excretion of

DDE in breast milk, which transfers a large

portion of the mother's DDE burden to the

young animal or child.

Possibly leading to reproductive issues in

adults as it mimics ESTROGEN hormone.

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DDT

• In 1962, Rachel Carson published Silent Spring

warning of the dangers.

• Banned in developed countries by late 1960’s;

still used in developing countries

• Today it is the most prevalent contaminant on

U.S. imported food!!!

• The example of DDT highlights a more general

problem with synthetic pesticides. Many of

them have proven to have unintended

consequences on non-target species.

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CURRENT PESTICIDE USE

• EPA estimates total pesticide use in the U.S.

amounts to about 5.3 billion pounds annually.

Roughly half is chlorine and hypochlorites

used for water purification

Roughly 80% of all conventional pesticides

applied in the U.S. are used in agriculture or

food storage and shipping.

Remainder are used as preservatives in

wood, leather and other materials

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USE OF PESTICIDES IN THE U.S.

Insect

repellants

like DEET

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PESTICIDE TYPES

• INORGANIC PESTICIDES – broad-spectrum, generally highly toxic, essentially indestructible (ie: arsenic, sulfur, copper, lead, mercury)

Generally NEUROTOXINS

Frequently used to cover seeds to deter

pests from eating them

Extremely dangerous to farm workers

Many have been banned

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PESTICIDE TYPES

• NATURAL ORGANIC PESTICIDES - generally plant extracts:

- Nicotine – toxic to insects & humans

- Rotenone – used to kill fish

- Pyrethrum & Turpentine – also used to preserve wood

Many have been banned due to their persistence & toxicity in the environment

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PESTICIDE TYPES

• FUMIGANTS - small molecules that gasify easily and penetrate materials rapidly.

• Can be used in soils and on grains

(ie: carbon tetrachloride, ethylene dibromide)

Extremely dangerous; many have been banned.

Again, extremely dangerous to workers,

many have been banned or restricted

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PESTICIDE TYPES

• CHLORINATED HYDROCARBONS –

• a.k.a. – Organochlorines

fast acting and highly toxic to sensitive organisms

Generally low toxicity for humans

Inhibit nerve membrane ion transport and block nerve signal transmission

Persistent and concentrate in food chains

(ie: DDT, mothballs, chlordane, dieldrin)

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PESTICIDE TYPES

• ORGANOPHOSPHATES - EXTREMELY toxic to mammals, birds and fish

(10-100x more toxic than chlorinated hydrocarbons)

Inhibit cholinesterase, an enzyme necessary for nervous system function

A single drop of TEPP can be lethal, very dangerous to workers in fields

Quickly degrade within hours-days

Many derived from nerve gas research!

ie: Malathion, parathion, DDVP, TEPP

GLYPHOSATE (“Roundup”) does not affect nervous systems. It is a general herbicide used with GMO resistant crops

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PESTICIDE TYPES • CARBAMATES – a.k.a. Urethanes

All are EXTREMELY TOXIC TO BEES

similar to organophosphates - highly toxic but very low bioaccumulation, degrade rapidly, low persistence

ie: Sevin, Temik, Zineb, Baygon, Mirex

• HALOGENATED PYRROLES - new class of compounds based on a MICROBIAL TOXIN. Marketed as “Pirate.”

Shown to reduce egg laying & survival in ducks even at low concentrations

Should be withdrawn – similar to DDT

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PESTICIDE TYPES

• BIOLOGICAL CONTROLS & MICROBIAL AGENTS - living organisms or toxins derived from them to be used in place of pesticides

Bacteria such as Bacillus thuringiensis (Bt) that kills beetles and caterpillars by rupturing the digestive tract when consumed.

Parasitic wasps such as Trichogramma kill moths caterpillars and eggs.

Ladybugs & Praying Mantis eat harmful insects which damage plants

Viruses have also been used against specific pests

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PESTICIDE BENEFITS

• DISEASE CONTROL -

• Many insects & ticks serve as disease vectors.

- Mosquito spreads Plasmodium protozoan

which causes malaria

- Mosquito borne VIRAL diseases: Yellow

Fever, Encephalitis, West Nile, Zika

- Trypanosomiasis protozoan causes

sleeping sickness spread by the Tsetse fly.

- Elephantatis caused by flies that spread

tiny round worms

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PESTICIDE BENEFITS

• CROP PROTECTION - Losses would be much

higher without pesticides.

Using pesticides, pre-harvest losses to

diseases and pests (insects/birds) are at 33%

Using pesticides, post-harvest losses at an

additional 20-30% from rodents, insects, fungi

In general, farmers save an average of $3-$5

for every $1 spent on pesticides.

Without using pesticides estimates of $21

billion annual losses in food & fiber (cotton)

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PESTICIDE PROBLEMS

• NON-TARGET SPECIES

Up to 90% of pesticides never reach intended

target and many beneficial organisms are

killed. (bees, birds, fish)

• PESTICIDE RESISTANCE

Resistant members of a population survive

pesticide treatment and produce more

resistant offspring.

- (1000 insects, 550 weeds have developed

chemical resistence)

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PESTICIDE PROBLEMS

• PEST RESURGENCE or PEST REBOUND

“Pesticide Treadmill” - as pests become

resistant, we must develop new, stronger

pesticides.

Some pests are gaining genetic resistance

via viruses that spread resistant DNA

EVERY PESTICIDE HAS A LIMITED TIME

OF EFFECTIVENESS BEFORE THE PEST

BECOMES RESISTANT OR INCREASING

ENVIRONMENTAL CONCENTRATIONS

CREATE PROBLEMS.

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CREATION OF NEW PESTS

• Broadcast spraying (wide range) is also likely to

kill beneficial predators (other insects that are

beneficial – wasps, mantis, ladybugs)

Under normal conditions many herbivorous

pests are controlled by natural predators.

When we kill the predators, we remove a

limiting factor and the pests increase.

• With the use of chemical pesticides, farmers

have abandoned traditional “natural” methods

of pest/pathogen control such as crop rotation.

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ENVIRONMENTAL PERSISTENCE AND

MOBILITY

• Because chlorinated hydrocarbons (ie: DDT)

are so persistent, they tend to show up far from

the point of dispersal.

Stored in fat and tend to bioaccumulate

Highly concentrated in higher trophic levels

(eagles, trout, whales, polar bears, humans)

- Accumulate in polar regions due to the

“GRASSHOPPER EFFECT”. Pesticides

evaporate from warm regions, condense

and end up in precipitation in colder

regions

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EXAMPLES OF PERSISTENCE

• Inuit women’s breast milk was 5x that of

Canadian women just 1600 miles south.

• Polar bears have 3x Billion more chlorinated

compounds that the sea water around them

• Beluga whale carcasses are treated as toxic

waste due to the level of chlorinated

hydrocarbons in their tissues.

• Human babies, exposed to DDT in the womb,

are often premature, have reduced weight &

fertility problems as adults.

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“POP’s TREATY”

• 12 PERSISTENT ORGANIC POLLUTANTS were banned globally in 2001 by 127 countries .

Use was previously banned or restricted in developed countries, but U.S. companies continued to sell POPs to underdeveloped countries where regulations were lax.

Many pesticides then returned to U.S. on agricultural products (fruit/veggies) and in migrating wildlife.

• Since the treaty banning POPs, other pesticides have taken their place.

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“POP’s TREATY” PERSISTENT ORGANIC POLLUTANTS

banned globally in 2001.

Aldrin

Chlordane

Dieldrin

DDT

Endrin

Hexachlorobenzene

Neptachlor

Mirex

Toxaphene

PCB’s (Polychlorinated biphenyls)

Dioxins

Furans

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HUMAN HEALTH PROBLEMS

• ACUTE EFFECTS: rapid effects resulting in poisoning & illness from exposure or high dose

• CHRONIC EFFECTS: after prolonged exposure, long-lasting effects such as cancer, birth defects, immunological problems, neurological problems, chronic degenerative diseases such as Parkinson’s.

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HUMAN HEALTH PROBLEMS

• WHO estimates 25 million people suffer pesticide poisoning, and 20,000 die each year.

At least 2/3 of these result from occupational hazards in developing countries.

Long-term health effects are difficult to conclusively document.

- Many people exposed to pesticides have other environmental exposure risks

(smoking, and chemical exposures from multiple sources (gasoline, solvents, different types of pesticides, etc)

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EXAMPLES OF HEALTH PROBLEMS

- PCBs in Great Lakes fish have been linked to learning deficiencies in children whose mothers ate fish years before the birth.

- Children whose homes are fumigated are 3x more likely to get acute lymphocytic leukemia.

- Greenhouse farmers in South America experience nausea, rashes, asthma, etc

- Children exposed to pesticides often have diminished memory and motor function

- Children are at greater risk to toxins. Can autism, hyperactivity & ADD be linked to environmental toxins?

.

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ALTERNATIVES TO PESTICIDE USE

• BEHAVIORAL CHANGES

Crop Rotation – reduces pests

Mechanical Cultivation – reduces herbicide use

but may increase erosion

Flooding Fields – reduces weeds and insects

Habitat Diversification – planting hedges, trees,

& ground cover can provide habitat for predators

of pests. (birds, owls, reptiles, Mantis, etc)

Growing in Pest-Free Zones

Adjusting Planting & Tillage Times

Plant Mixed Polycultures – many crops

grown together keeps pest numbers low

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BIOLOGICAL CONTROLS

• Predators or pathogens

• Insects that eat weeds

• Plants like the Neem tree that

make their own pesticides

• Bioengineering pest resistant crops

• Release of sterile male insects

• Hormones that disrupt

development or attract

insects to traps (broad

use of hormones could

affect non-target species)

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INTEGRATED PEST MANAGEMENT – (IPM)

• Flexible, ECOLOGICALLY-BASED STRATEGY that uses a combination of techniques applied at specific times aimed at specific pests

Tries to minimize use of chemical controls and avoids broad spectrum controls

Uses preventative practices to encourage beneficial organisms and enhance plant defenses

Balances economic losses with the ultimate use of chemical controls.

Time, type & method of application are critical

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INTEGRATED PEST MANAGEMENT

• TRAP CROPS - small areas planted before the

main crop. These plants mature first and attract

the insects, and the trap crop is then sprayed

heavily to destroy pests. Crop is cut down &

not sold. Worker risk is also minimized.

• Introduction of BIOLOGICAL CONTROLS are

also used successfully in IPM. But, must be

used carefully so that introduced organisms do

not become pests themselves.

• IPM is being used successfully all over the

world. Cuts pesticide use while maintaining

yield.

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WHAT DO YOU THINK?

READ THE ARTICLE

PAGE 221

IN YOUR TEXTBOOK:

ORGANIC FARMING IN CUBA

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IPM PROGRAM IN INDONESIA

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REASONS TO REDUCE

PESTICIDE EXPOSURE

• 2.4 million metric tons used annually in the US

• 600 active ingredients,

• 1200 “inactive” ingredients

• Less than 10% of active pesticide ingredients

have been subjected to a full battery (ten tests)

of chronic health-effect tests.

OF THE 321 PESTICIDES SCREENED, EPA

REPORTS 146 ARE PROBABLE HUMAN

CARCINOGENS.

• Since 1972, only 40 pesticides have been

banned.

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WHO REGULATES PESTICIDES IN THE US?

• (EPA) Environmental Protection Agency

regulates sale & use, and sets tolerance levels

• (FDA) Food and Drug Administration and the

(USDA) Department of Agriculture enforce

pesticide use and tolerance levels set by EPA.

Can seize and destroy food in violation of laws.

FIFRA – Federal Insecticide, Fungicide, and

Rodenticide Act – mandates “registration of

all pesticides

FFDCA – Federal Food, Drug, and Cosmetic

Act sets “tolerance” levels for pesticides that

remain on foods sold in the US.

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CHILDREN & PESTICIDE EXPOSURE

• Studies show children are more susceptible

than adults to toxic pesticides.

Pound for pound kids eat more food,

drink more water and breathe more air

Play on surfaces that accumulate

pesticides (grass, dirt)

Put fingers in mouths, don’t wash hands

Exposed during vulnerable growth &

developmental stages

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FOOD QUALITY PROTECTION ACT - 1996

• FQPA required the EPA to evaluate ingredients in pesticides and set exposure levels for infants and children. (Prior, most evaluations were conducted based on adult exposure)

• Out of 2,500 “inert” ingredients, 650 were found to be hazardous. 50% were classified as carcinogens, and/or occupational hazards.

• EPA banned use of methyl parathion on all fruits & many vegetables

• Prohibited use of the insecticide Dursban found in 20% of residential use products.

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REGULATING PESTICIDES

• TREATED LUMBER/WOOD

• Late 1900’s creosote and tar were used to treat lumber to reduce termite, fungus, etc. Both are extremely toxic and slow to degrade.

• Chromated Copper Arsenate (CCA) was then used in pressure treated lumber used in play equipment and decks. CCA was banned for residential use in 2003 due to the ARSENIC

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REGULATING PESTICIDES

38% of fruits and 12%

of U.S. vegetables are

imported.

2% are inspected by

the FDA

Less than 0.2% is

inspected for microbes

or pesticides, which are

widely used in

developing nations.

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IS ORGANIC THE ANSWER?

• Numerous studies have shown organic, sustainable agriculture is more eco-friendly and leaves soil healthier than intensive, chemical-based mono-culture cropping.

Currently, less than 1% of all American farmland is organic but market is growing.

Organic food must be produced without the use of hormones, antibiotics, pesticides, synthetic fertilizers or genetic modification.

Animals must be raised on organic feed, given access to the outdoors, given no steroids or growth hormones and given antibiotics only to treat disease.

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IS ORGANIC THE ANSWER?

• Critics are disappointed by limited scope of the definition of organic. They hope to include:

Growing food in harmony with nature

Food distribution based on co-ops, farmer’s markets, and local production

Food should be simple, wholesome, nutritious. At present, processed ingredients are allowed in organic food.

• Some doubt whether organic growers can produce enough to feed everyone.

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REDUCING YOUR OWN RISKS

• Wash all fresh fruits and vegetables well

• Peel fruits and vegetables

• Discard outer leaves of lettuce

• Avoid prolonged storage of fresh foods

• Cooking may degrade some pesticides

• Trim fat from meats to reduce

bioaccumulated chemicals

• Ask for and buy organically grown food.

Simple economics – supply and demand will

bring down costs.