PEST CONTROL
Chapter 10
Biological pests are organisms that reduce the availability, quality or value resources useful to
humans.
Insects are the most frequent pests but birds, small mammals and other invertebrates animals
as well as some plant species could be pests
Pesticide is a chemical that kills pests. The following are some pesticides:
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Biocides kill a broad spectrum of organisms.
Herbicides kill plants.
Insecticides kill insects (larvacide, adulticide).
Fungicides kill fungi.
Rodenticides kill rodents.
HISTORY OF PEST CONTROL
1) Sumerians controlled insects with sulfur 5000 years ago.
2) Chinese texts 2500 years ago describe mercury and arsenic compounds used to control body
lice and other pests.
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They introduced 120 years ago predatory insects and plant derived insecticides into
their orchards for protection of their crops.
3) Greeks and Romans used ash, sulfur and oil sprays to protect themselves, livestock and
crops from pests.
4) The Swiss chemist Paul Muller discovered DDT in 1934.
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Toxic to insects by relatively nontoxic to mammals.
The oral dose for humans is LD50 for humans is 113 mg/kg.
Compared with an LD50 of 50 mg/kg for nicotine.
Commercial production began in 1943.
He received the Nobel price in 1948 for the discovery of DDT.
Current Pesticide Use
5) United States used 5.3 billion pounds (2.4 million metric tons) of pesticides in 1999 or 20% of
the world consumption.
 Most of the pesticides are chlorine compounds used in water purification, 49.1%.
 Other pesticides are wood preservatives 15.1%; conventional pesticides 23.3%;
specialty biocides (preservatives, sealants, etc) 6.4%; other (sulfur, petroleum, etc.)
6.2%.
 In the US 80% of pesticides are used in agriculture, food storage and shipping.
 Homes and gardens account for 8% of the pesticides used in US.
 Italy and Germany use about one fifth as much.
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Canada uses about one tenth as much.
About 90% of all pesticides worldwide are used in agriculture or food storage and
shipping.
Herbicides, 59%; insecticides, 22%; fungicides, 11%.
PESTICIDE TYPES:
Inorganic pesticides: arsenic, mercury, copper, lead. Highly toxic indestructible biocides; most
of them are neurotoxins and a single dose can cause permanent damage.
Natural organic pesticides or "botanical": nicotine, alkaloids, pyrethrum, turpentine, and
phenols. Extracted from plants. Some are biocides.
Fumigants: carbon tetrachloride, ethylene dichloride, ethylene dibromide, etc. They gasify
easily and are extremely dangerous to humans and animals. Most have been banned.
Chlorinated hydrocarbons: DDT, chlordane, aldrin, mothballs, etc. They are synthetic organic
insecticides that affect neural signal transmission. They persist in the soil for many years
and accumulate in fatty tissues. Many have been banned.
Organophosphates: parathion, melathion, dichlorvos, TEPP, etc. Extremely toxic to mammals,
birds and fish. are derived from alkaloids and are an outgrowth of nerve gas research
during WWII. They inhibit a n enzyme needed to for removing excess neurotransmitter
from synapses in the peripheral nervous system. They are extremely toxic; a drop of
TEPP on the skin can kill a human. They are used a herbicides and are biodegradable.
Carbamates or urethanes are similar to organophosphate including mode of action, toxicity and
low bioaccumulation.
Microbial agents and biological control. They are living organisms or toxins derived from
them. The BT used by the Pest Control Center in Memphis is derived from Bacillus
thuringiensis.
Halogenated pyrroles are a new class of compounds based on naturally occurring microbial
toxin. They have been considered to be a replacement for organophosphates. They
reduce egg laying and egg survival in ducks.
PESTICIDE BENEFITS
Humans compete with other species for food and shelter, and struggle to protect ourselves from
disease.
1) Disease control.
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Insects, ticks, lice, etc. are vectors of diseases.
2) Crop protection.
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Postharvest losses often amount to 30% of the harvest.
Cosmetic damage is reduced.
PESTICIDE PROBLEMS
1) Effects on nontarget species.
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Estimated that 90% of the pesticide does not reach their target.
Many beneficial organisms are killed, e. g. honeybees.
2) Pesticide resistance and pest resurgence.
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Pesticides seldom kill 100% of the target species.
Pesticide treadmill: constantly increasing doses, or use newer or more toxic chemicals in
order to obtain the same result
Resistance transfer from one species to another.
3) Creation of new pests.
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Beneficial predators keep the prey numbers down.
When predators are killed, prey may become a pest.
Higher trophic levels are more likely to be affected by pesticides.
4) Persistence and mobility in the environment.
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Bioaccumulation, ground water contamination.
Wind, rain, etc. transport pesticide residue to distant places.
5) Human health problems.
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Cancer, birth defects, immunological problems are long term effects.
Short-term effects include acute poisoning and illness.
ALTERNATIVES TO PESTICIDES
1) Behavioral changes.
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Crop rotation keeps pest populations from building up.
Habitat diversification: hedgerows, windbreaks, etc
Flooding fields and burning crop residues before planting.
2) Biological controls.
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Predators: wasps, ladybugs, praying mantises, and pest pathogens.
Insect repelling plants: marigolds, garlic, basil and peppermint.
Genetic engineering, e. g. sterile males, resistant species.
3) Integrated Pest Management (IPM).
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Uses a combination of techniques applied at specific times.
Mechanical means, minimum use of pesticides.
Pest monitoring to determine economic threshold, the point when potential economic
damage justifies pesticide.
REGULATING PESTICIDES
Over 500,000 metric tons of pesticides are used in the United States every year.
These pesticides contain over 600 active ingredients combined with 1200 presumably inactive
carriers, solvents, preservatives, etc.
They are marketed in about 25,000 commercial products.
Three federal agencies share the responsibility for regulating pesticides used in food production.
These federal agencies are:
1) Environmental Protection Agency (EPA).
It regulates the sale and use of pesticides.
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The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) regulates the sale
and use of pesticides. It mandates the registration (licensing) of the substance.
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Federal Food, Drug and Cosmetic Act (FFDA) sets tolerance levels or limits on the
amount of pesticide residue may remain on or in foods.
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Based on scientific studies, the EPA determines which pesticides will not pose
significant risks to human health or the environment when used according to label
directions.
2) Food and Drug Administration (FDA).
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Enforce pesticide and use and tolerance levels set by the EPA.
3) Department of Agriculture (USDA).
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Enforce pesticide and use and tolerance levels set by the EPA.
In Canada, Agriculture Canada performs functions similar to the EPA through the Pest Control
Products Act and Regulations.
The Food Quality Protection Act passed by Congress in 1996 directs the EPA to pesticide
tolerance levels based on potential aggregate pesticide exposures
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This Act requires that the EPA reassess 9,700 pesticides by 2006 in order to include
their cumulative impact on children.
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Inert ingredients are used to dilute or transport the pesticides. Under this Act inert
ingredients will be also assessed for their impact on humans. About half of the inert
ingredients that have been studied are carcinogenic, occupation hazards, or air and
water pollutants
The EPA is also studying hormone-disrupting chemicals.
Wood preservatives are pesticides especially dangerous to children. These preservatives
prevent the growth of molds, invasion by termites, etc.
38% of the fruit and 12% of the vegetables consumed in the US come from abroad but only
about 2% of these are inspected by the FDA.
The Province of Quebec, Canada, has banned the use of most non-farm pesticides in the
province beginning in 2005.
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Many people fear the we are exposed to too many dangerous chemicals.
Industry claims that it cannot operate without them.
Eating organic food does no protect the individual from all risks. Microbes are present in
organic food.