Classification of Pesticides

The U.S Environmental Protection Agency (EPA) defines a pesticide as “any

substance or mixture of substances intended for preventing, destroying,

repelling, or mitigating any pest”.

A pesticide may be a chemical substance or biological agent (such as a virus

or bacteria) used against pests including insects, plant pathogens, weeds,

mollusks, birds, mammals, fish, nematodes (roundworms) and microbes that

compete with humans for food, destroy property, spread disease or are a

nuisance. Many pesticides, mainly chemical pesticides, are poisonous to

humans.

General Information

Types of Pesticides

• Bactericides for the control of bacteria

• Herbicides for the control of weeds

• Fungicides for the control of fungi

• Insecticides for the control of insects - these can be Ovicides, Larvicides or Adulticides

• Miticides for the control of mites

• Nematicides for the control of worms

• Rodenticides for the control of rodents

• Virucides for the control of viruses

Pesticides can also be classed as synthetic pesticides or biological pesticides, although the distinction can

sometimes blur.

A systemic pesticide is a pesticide applied to a plant which is absorbed into its sap and so distributed

throughout the plant to make all parts of it poisonous to pests, without harming the plant, although systemic

insecticides which poison pollen and nectar in the flowers may kill needed pollinators.

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History

Since before 500 BC, humans have used pesticides to prevent damage to their crops. The first known pesticide

was sulfur. By the 15th century, toxic chemicals such as arsenic,

mercury and lead were being applied to crops to kill pests. In the 17th

century, nicotine sulfate was extracted from tobacco leaves for use as

an insecticide. The 19th century saw the introduction of two more

natural pesticides, pyrethrum which is derived from chrysanthemums,

and rotenone which is derived from the roots of tropical vegetables.

In 1939, Paul Müller discovered that DDT was a very effective

insecticide. It quickly became the most widely-used pesticide in the

world. However, in the 1960s, it was discovered that DDT was preventing many fish-eating birds from

reproducing which was a huge threat to biodiversity. Rachel Carson wrote the best-selling book “Silent Spring”

about biological magnification. DDT is now banned in at least 86 countries, but it is still used in some

developing nations to prevent malaria and other tropical diseases by killing mosquitos and other disease-

carrying insects.

Pesticide use has increased 50-fold since 1950, and 2.5 million tons of industrial pesticides are now used each

year.

Regulation

In most countries, in order to sell or use a pesticide, it must be

approved by a government agency. For example, in the United

States, the EPA does so. Complex and costly studies must be

conducted to indicate whether the material is effective against the

intended pest and safe to use. During the registration process, a

label is created which contains directions for the proper use of the

material. Based on acute toxicity, pesticides are assigned to a

Toxicity Class. Pesticide misuse is illegal in most countries.

Some pesticides are considered too hazardous for sale to the general public and are designated restricted use

pesticides. Only certified applicators, who have passed an exam, may purchase or supervise the application of

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restricted use pesticides. Records of sales and use are required to be maintained and may be audited by

government agencies charged with the enforcement of pesticide regulations.

“Read and follow label directions” is a phrase often quoted by extension agents, garden columnists and others

teaching about pesticides. This is not merely good advice; it is the law, at least in the U.S. Similar laws exist in

limited parts of the rest of the world. The Federal Insecticide, Fungicide, and Rodenticide Act of 1972 (FIFRA)

set up the current system of pesticide regulations. It was amended somewhat by the Food Quality Protection Act

of 1996. Its purpose is to make pesticide manufacture, distribution and use as safe as possible. The most

important points for users to understand are these: it is a violation to apply any pesticide in a manner not in

accordance with the label for that pesticide, and it is a crime to do so intentionally.

Effects of pesticide use

On the environment

Pesticides have been found to pollute virtually every lake, river and stream in the United States, according to the

US Geological Survey. Pesticide runoff has been found to be highly lethal to amphibians, according to a recent

study by the University of Pittsburgh. Pesticide impacts on aquatic systems are often studied using a hydrology

transport model to study movement and fate of chemicals in rivers and streams.

The use of pesticides also decreases biodiversity in the soil. Not using them results in higher soil quality with

the additional effect that more life in the soil allows for higher water retention. This helps increase yields for

farms in drought years where there is less rain. For example, during drought years, organic farms have been

found to have yields 20-40% higher than conventional farms.

On farmers

There have been many studies of farmers with the goal of determining the health effects of pesticide exposure.

Research in Bangldesh suggests that many farmers’ do not need to apply pesticide to their rice fields, but

continue to do so only because the pesticide is paid for by the government. Organophosphate pesticides have

increased in use, because they are less damaging to the environment they are less persistent than organochlorine

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pesticides. These are associated with acute health problems such as abdominal pain, dizziness, headaches,

nausea, vomiting, as well as skin and eye problems. Additionally, many studies have indicated that pesticide

exposure is associated with long-term health problems such as respiratory problems, memory disorders,

dermatologic conditions, cancer, depression, neurologic deficits, miscarriages, and birth defects. Summaries of

peer-reviewed research have examined the link between pesticide exposure and neurologic outcomes and

cancer, perhaps the two most significant things resulting in organophosphate-exposed workers.

On consumers

A study published by the United States National Research Council in 1993 determined that for infants and

children, the major source of exposure to pesticides is through diet. A recent study in 2006 measured the levels

of organophosphorus pesticide exposure in 23 school children before and after replacing their diet with organic

food (food grown without synthetic pesticides). In

this study it was found that levels of

organophosphorus pesticide exposure dropped

dramatically and immediately when the children

switched to an organic diet.

Dangers of pesticides

Pesticides can present danger to consumers,

bystanders, or workers during manufacture,

transport, or during and after use. There is concern

that pesticides used to control pests on food crops

are dangerous to the consumer. These concerns are one reason for the organic food movement. Many food

crops, including fruits and vegetables, contain pesticide residues after being washed or peeled. Residues,

permitted by US government safety standards, are limited to tolerance levels that are considered safe, based on

average daily consumption of these foods by adults and children.

Tolerance levels are obtained using scientific risk assessments that pesticide manufacturers are required to

produce by conducting toxicological studies, exposure modelling and residue studies before a particular

pesticide can be registered, however, the effects are tested for single pesticides, and there is no information on

possible synergistic effects of exposure to multiple pesticide traces in the air, food and water.

The remaining exposure routes, in particular pesticide drift, are potentially significant to the general public.

Risk of exposure to pesticide applicators, or other workers in the field after pesticide application, may also be

significant and is regulated as part of the pesticide registration process.

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Children have been found to be especially susceptible to the harmful effects of pesticides. A number of research

studies have found higher instances of brain cancer, leukemia and birth defects in children with early exposure

to pesticides, according to the National Resources Defense Council.

Besides human health risks, pesticides also pose dangers to the environment. Non-target organisms can be

severely impacted. In some cases, where a pest insect has some controls from a beneficial predator or parasite,

an insecticide application can kill both pest and beneficial populations. The beneficial organism almost always

takes longer to recover than the pest. Pesticides sprays in an effort to control adult mosquitoes, may temporarily

depress mosquito populations, however they may result in a larger population in the long run by damaging the

natural controlling factors.

Pesticides inflict extremely widespread damage to biota, and

many countries have acted to discourage pesticide usage through

their Biodiversity Action Plans. Misuse of pesticides can also

cause pollinator decline, which can adversely affect food crops.

An early discovery relating to pesticide use, is that pests may

eventually evolve to become resistant to chemicals. When

sprayed with pesticides, many pests will initially be very

susceptible. However, not all pests are killed, and some with

slight variations in their genetic make-up are resistant and therefore survive. Through natural selection, the pests

may eventually become very resistant to the pesticide. Farmers may resort to increased use of pesticides,

exacerbating the problem.

‘’Persistent Organic Pollutants’’ (POPs) are one of the lesser-known environmental issues raised as result of

using pesticides. POPs may continue to poison non-target organisms in the environment and increase risk to

humans by disruption in the endocrine system, cancer, infertility and mutagenic effects, although very little is

currently known about these ‘chronic effects’. Many of the chemicals used in pesticides are persistent soil

contaminants, whose impact may endure for decades, and adversely affect soil conservation.

A new study conducted by the Harvard School of Public Health in Boston, has discovered a 70% increase in the

risk of developing Parkinson’s disease for people exposed to even low levels of pesticides.

Managing pest resistance

Pest resistance to a pesticide is commonly managed through pesticide rotation or tankmixing with other

pesticides.

Rotation involves alternating among pesticide classes with different modes of action to delay the onset of or

mitigate existing pest resistance. Different pesticide classes may be active on different pest sites of action. The

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U.S. Environmental Agency (EPA or USEPA) designates different classes of fungicides, herbicides and

insecticides. Pesticide manufacturers may, on product labeling, require that no more than a specified number of

consecutive applications of a pesticide class be made before alternating to a different pesticide class. This

manufacturer requirement is intended to extend the useful life of a product.

Tankmixing pesticides is the combination of two or more pesticides with different modes of action. This

practice may improve individual pesticide application results in addition to the benefit of delaying the onset of

or mitigating existing pest resistance.

Continuing development of pesticides

Pesticides are often highly efficient for producers who are in the business

of large scale agriculture. Pesticide safety education and pesticide

applicator regulation are designed to protect the public from pesticide

misuse, but do not eliminate all misuse. Reducing the use of pesticides

and replacing high risk pesticides is the ultimate solution to reducing

risks placed on our society from pesticide use. For over 30 years, there

has been a trend in the United States and in many other parts of the

world to use pesticides in combination with alternative pest controls.

This use of integrated pest management (IPM) is now commonplace in

US agriculture. With pesticide regulations that now put a higher priority

on reducing the risks of pesticides in our food supply and emphasize environmental protection, old pesticides

are being phased out in favor of new reduced risk pesticides. Many of these reduced risk pesticides include

biological and botanical derivatives and alternatives. As a result, older, more hazardous, pesticides are being

phased out and replaced with pest controls that reduce these health and environmental risks. Chemical engineers

continually develop new pesticides to produce enhancements over previous generations of products. In addition,

applicators are being encouraged to consider alternative controls and adopt methods that reduce the use of

chemical pesticides. This process is on-going and is not an immediate solution to the risks of pesticide use.

In 2006, the World Health Organization suggested the resumption of the limited use of DDT to fight malaria.

They called for the use of DDT to coat the inside walls of houses in areas where mosquitoes are prevalent. Dr.

Arata Kochi, WHO’s malaria chief, said , “One of the best tools we have against malaria is indoor residual

house spraying. Of the dozen insecticides that has approved as safe for house spraying, the most effective is

DDT.”

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INORGANIC PESTICIDES

The inorganic pesticides are those pesticides that do not contain

carbon. They can contain elements or natural compounds, such

as arsenic, copper, boron, mercury, sulfur, tin, zinc, borate,

diatomite, silica or other substances. Many of the organics were

important early pesticides, but many have since been banned or severely curtailed because of health and

environmental concerns. A few inorganic pesticides are used in urban pest situations as alternatives to organic

pesticides because of their relatively low risk to humans and animals. One of these includes the borates (i.e.

boric acid) that have a low acute toxicity to humans and animals, but are very toxic to certain insects. Even with

the borates, care must be taken when using dust formulations around people with chronic respiratory ailments,

such as asthma. A second group of low risk inorganic pesticides are the insect desiccants. This group of

pesticides contains silica aerogel or diatomaceous earth. They absorb oils from the exoskeleton (cuticle) of

insects or physically damage the cuticle causing water loss and death because the insects cannot live without

water.

The first chemicals used in weed control were inorganic compounds. Among them were the trivalent arsenicals,

borate compounds, ammonium salts and sodium chlorate. A few of the inorganic herbicides are still used in

weed and brush control, but most have been replaced by organic compounds because of the persistence of the

inorganics in soils and their toxicity to humans and wildlife.

Scientists recognized the need to overcome the damage that insect pests and diseases caused farmers and

gardeners and developed pesticides that would eradicate or limit the insects and diseases that damaged or ruined

their crops.

Insecticides. These products kill a wide range of insects, either by contact or by ingestion by the target insect.

The more commonly found insecticides are acephate (Orthenex), carbaryl (Sevin), Malathion, Imidicloprid

(Merit or Tree and Shrub Insect Control) or pyrethroids (synthetic versions of plant-based pyrethrins, includes

cyfluthrin and permethrin).

Miticides. Mites are not true insects, as they have eight legs, no antennae or true jaws. Almost microscopic in

size, they cause a lot of damage. Among the well-known mites are the red spider mites, russet (or rust) and the

citrus bud mite. Sprays containing ethion, an organic phosphate, are commonly used to control mites.

Herbicides. These chemicals kill weeds and plants by disrupting a phase in their growth. Some are selective,

killing only a certain type of weed (broad-leaved, grasses) while others will kill anything that the spray contacts.

Glyphosate (Roundup, etc.), glufosinate-ammonium (Finale), sethoxydim (Grass Getter), 2,4-D/2,4-DP (Brush

Buster) and triclopyr (Brush Killer) are currently on the market.

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Fungicides. Rusts and powdery mildews on roses and many, many other popular plants cause discoloration and

deformation (curling) of the leaves. In some cases a fungal infection can cause the complete loss of leaves

(defoliation). There are hundreds of known fungi that attack plants, either above ground or through the roots of

susceptible plants (for example, oak root fungus). Tribasic copper sulfate (Micro-Cop and Liqui-Cop) is widely

used in fungicides.

Molluscicides. Snail baits can be in a granular, pellet or liquid form. They usually contain metaldehyde, a

chemical that dehydrates slugs and snails when eaten.

Bactericides. Bacteria cause gummosis in fruit and nut trees. These microscopic animals can also attack many

flowers, shrubs and trees in the landscape and in houseplants. Tribasic copper sulfate (Micro-Cop) helps control

many outbreaks but some bacterial infections resist control.

Nematicides. Nematodes are microscopic worms that live in the soil, feeding on plant roots, damaging or

stunting them. A few species feed on plant stems and leaves. Severe infestations can lead to the death of a plant

due to the inability of the plant to supply insufficient amounts of moisture and nutrients. There are no products

on the market for homeowner use in controlling nematodes. Soil sterilization is sometimes used to control

nematodes.

ORGANIC PESTICIDES

Organic pesticides are compounds used to control pests that contain carbon. Although organic pesticides can

occur naturally, they are most often human-made (synthetic). They get their name based on some aspect of their

chemistry. For example organophosphate pesticides contain phosphorus

and carbamate pesticides and have a carbamic acid base.

Over the centuries, since the raising of food became the chief means of

survival, farmers have tried using many plants or their extracts to eradicate the insects and diseases that ravaged

their crops. An organic (natural) pesticide is one that has components found in plants, animals or minerals, or

whose action is a result of a biological process such as Bacillus thuringiensis, or commonly known as “Bt”.

Be aware that an “organic” or “natural” pesticide does not mean harmless to humans if the concentrate or spray

is inhaled, ingested, gets into the eyes, on the skin or used incorrectly.

INSECTICIDES

Horticultural oils. Horticultural oil (highly refined petroleum product such as Volck Oil), mineral oil, garlic oil,

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used by organic gardeners. Oils suffocate the insect and must contact and cover the insect to be effective. Some

fungicidal effects are also claimed with the use of some oils.

Insecticidal soap (not a true soap, but the potassium salts of fatty acids found in animal fats and plant oils).

Some use homemade detergent mixtures. Soaps, either commercial products or homemade, enter the breathing

tubes of insects, causing their collapse and the death of the insect.

Sabadilla. Made from the seeds of Schoenocaulon officinale of Venezuela, containing alkaloids. It is used as

dust. Moderately toxic to honeybees, mammals and causes violent allergic reactions in susceptible individuals.

It is effective on a wide range of insect larva and adults.

Boric acid. Very effective when combined with a food that attracts ants and cockroaches. Commercially made

traps are available or you can make your own.

Ryania. From the shrub Ryania speciosa and sold as a dust. It is touted as a broad-

spectrum insecticide. Often found in mixtures of ryania, pyrethrin and rotenone.

Rotenone. Extracted from a variety of plants and once very popular, but because

of new products available and rotenone’s deadly poisonous nature, is now seldom

used.

Pyrethrins or Pyrethrum. The Pyrethrum daisies (Chrysanthemum cinerarariifolium and C. coccinium) contain

compounds that kill insects on contact. Pyrethrins are effective broad-spectrum insecticides and can safely be

used in the garden, on vegetables and on fruit trees. These sprays and dusts are often mixed with sulfur or other

compounds, giving them fungicidal properties or with other botanical insecticides. The products containing

pyrethrins are commonly found.

Nicotine sulfate. Known for decades by gardeners and farmers as Black Leaf 40, this highly poisonous

insecticide is extracted from a tobacco selected for its high nicotine content. Nicotine is highly toxic to

mammals when taken internally or absorbed through the skin. You must wear protective clothing, including

gloves, goggles and a respirator when spraying this insecticide.

Lime. An old-time insecticide. Wear protective gear, including gloves, goggles and a respirator when applying

to prevent inhalation of the dust.

Ammonia. Household ammonia is used to control many insects, but refrain from use in hotter weather.

Ammonia may injure the leaves of some plants so test before usage.

Quassia. From the wood and bark of the Quassia amara or Bitterwood tree. Typically, the bark and wood chips

are spread over the soil or are ground up to make sprays.

Alcohol. The sprays containing 70% isopropyl alcohol (rubbing alcohol) are used outdoors and indoors on

waxy-foliaged houseplants, controlling many sucking insects.

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Attractants: These natural products, usually sex pheromones, are the chemical signals used by insects to attract

mates. Attractants are used to trap insects and as mating disruption lures (they emit vast amounts of odors,

making it difficult for the males to find the females).

Bacillus thuringiensis (commonly called “Bt”). Probably the most widely used (there are over 35 varieties of

this bacteria) biological control. After Bt is sprayed on the plant caterpillar pests (includes cabbage loopers,

codling moth larvae, imported cabbage worms, spruce budworms, diamondback moths, gypsy moth larvae,

tomato hornworms and others) ingest it as they feed. It does not kill the insect or larva immediately, but the

insect stops feeding. It may live for several more days, but soon darkens, dies and drops to the ground.

ORGANIC FUNGICIDES

Mildews, scabs, rots and rusts disfigure many flowers, shrubs, shade trees and fruit trees. Farmers and gardeners

have used some of these fungicides for many years, long before any inorganic fungicides were developed. As

with insecticides, exercise caution when using, following directions explicitly as stated on the label.

Sulfur. One of the longest in use, sulfur is used to control both insects and

as a fungicide. It is considered a protectant fungicide. It is sold as a dust

(containing a small amount of clay or talc to enhance dusting qualities)

and as a wettable powder (it has a wetting agent added). Do not use sulfur

when the temperatures exceed 80 degrees F. Use only plastic sprayers, as

sulfur corrodes metals. Use protective gear when dusting or spraying.

Lime-sulfur. When lime is added to sulfur the fungicidal qualities of sulfur

is enhanced. Lime lets the sulfur penetrate the tissues, becoming an eradicant, killing recently germinated fungal

spores. The addition has a downside, the possibility of plant damage. Test the spray (or dust) on a small section

of the plant. Do not use when the temperatures exceed 85 degrees F. When using, wear protective gear,

including gloves and goggles.

Bordeaux mix. This old-time fungicide is a mix of copper sulfate and hydrated lime. Used as a spray or in

wettable powder form and has insecticidal and insect repellent properties. Bordeaux mix controls many plant

diseases, such as mildews, rusts, leaf curl, fire blight and some bacterial diseases. Read and follow label

directions carefully, refraining from use when temperatures are below 50 degrees F. and testing for possible

foliar damage.

Baking soda. Used as an eradicant, killing organisms that infect a plant as well as being a protectorant. Its

qualities are enhanced with the use of horticultural oil in equal amounts and mixed with water.

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Copper. Has been used since the invention of the printing press as pesticide, exhibiting fungicidal as well as

herbicidal properties. Copper inactivates enzyme systems in fungi, algae and plants. Copper is toxic to humans

and other mammals so use protective gear when using.

Compost tea. A solution concocted from finished, manure-based compost does double duty, feeding the plants

and serving as a fungicide. The tea is said to outcompete the troublesome fungi, such as powdery mildew and

botrytis blight, thereby inhibiting their growth.

Synthetic Organic Pesticides

Synthetic organic pesticides do not naturally occur in the environment, but are synthesized by man. They are

called organic compounds because they contain carbon and hydrogen atoms as the basis of their molecular

structure. The synthetic organic compounds include most of the insecticides, herbicides, rodenticides, avicides,

and other pesticides currently available.

There are five basic groups of synthetic organic insecticides that can be used in urban pest situations, including

schools. These include the chlorinated hydrocarbons, organophosphates, carbamates, pyrethroids, and

fluorinated hydrocarbons. There is an even larger number of synthetic organic herbicide classes and individual

ingredients available for control of weeds in crops, in turf, and other non-cropping areas. Some of these are used

around schools to control various weeds in turf, on parking lots, along fencelines, and around playgrounds.

Synthetic organic pesticides are also used to control rodents in, and around, schools. A few are even used to

control birds.

Chlorinated Hydrocarbons

This large group of insecticides varies considerably in their toxicity to mammals. Many of the chlorinated

hydrocarbon insecticides are prohibited from use in the United States. Their prohibition is primarily due to their

persistence in the environment and ability to accumulate in the fatty tissues of birds and mammals. Examples of

the prohibited pesticides within this group include DDT, chlordane, dieldrin, endrin, mirex and heptachlor.

Members of this group that continue to have registered uses in the US include lindane, dicofol, and

methoxychlor. Methoxychlor pesticide products are still available in a variety of formulations for control of

various indoor and outdoor insects. Use of methoxychlor and the less persistent and newer synthetic pyrethroid

and fluorinated hydrocarbon pesticide products have largely replaced other chlorinated hydrocarbon-containing

pesticide products in schools and other sensitive areas.

Organophosphates

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The organphosphates are a large group of pesticides containing about 39 active ingredients, which vary from

being moderately to very toxic to mammals. Organophosphates were the first insecticides used on a large scale

to replace the chlorinated hydrocarbons. Unlike most of the

chlorinated hydrocarbons, organophosphates are not stored in the

body for long periods of time. This property, combined with a

much shorter residual life also reduces the chances of long-term

environmental contamination. Many insect species world wide,

including flies mosquitoes, and cockroaches, have developed

resistance to the organophosphate insecticides because of their

frequent use and similar modes of action.

Organophosphates work by interfering with the activity of an enzyme, cholinesterase, which is necessary for

proper nerve function. Without this enzyme, impulses continue to pass down the nerve fiber disrupting the

nervous system and ultimately resulting in death by respiratory failure. Some of the more toxic

organophosphate insecticides can present a high risk of irreversible organophosphate poisoning in humans, from

excessive exposure. This risk is highest to pesticide applicators and non-target animals. Organophosphates,

unlike the organochlorines insecticides, do not accumulate in the tissues of humans or animals.

Many uses of organophosphates are being replaced by the pyrethrins, synthetic pyrethroids and the fluorinated

baits. However, certain organophosphates still have use in low-impact pesticide applications.

Carbamates

Carbamates are another large group of insecticides, a few of which are commonly used in the structural pest

control industry and around schools. Like the organophosphates, many of the carbamate insecticides used in

school, except perhaps for bendiocarb (Ficam) and propoxur (Baygon), are being replaced by the fluorinated

hydrocarbon baits and pyrethroids. Like the organophosphates, carbamates are cholinesterase inhibitors,

however their inhibition of this enzyme is reversible. Therefore, compared to the organophosphates, people

excessively exposed to carbamates have a greatly reduced likelihood of acute nerve poisoning and a greatly

increased recovery rate. Carbamates, like organophosphates, do not accumulate in the environment or fatty

tissues of mammals. Both carbamates and organophosphates act as contact insecticides with some stomach

poisoning activity. In addition to their use as insecticides, a number of carbamates are also used as herbicides

and fungicides. Bendiocarb and propoxur are two carbamate insecticides that continue to be used indoors in

schools in low-impact situations. Bendiocarb is very effective against ants, bees and wasps and is useful for

crack and crevice applications. Propoxur is effective on a variety of flying and crawling insects found in and

around school buildings. It is labeled for crack and crevice treatments in food handling situations and it is

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available in baits and many other formulations. Carbraryl (Sevin) dusts, wettable powders and aerosol

formulations continue to be used around schools, mostly outdoors, for controlling various turf, ornamental and

invasive insect pests.

Synthetic Pyrethroids

The synthetic pyrethroids or pyrethroids have a long and successful history in pest control. For ease of

classification they are placed in two categories or generations.

First generation pyrethroids have many of the same characteristics as pyrethrum, but are more stable, have

greater killing power, and are somewhat less irritating to the eyes and skin. Some first generation pyrethroids

commonly used to control pests in schools include: phenothrin/d-phenothrin (many), resmethrin/transresmethrin

(Endal), s-bioallethrein (many) and tetramethrin (many). Although some pesticide products contain only a first

generation ingredient most products containing first generation pyrethroids are combination products. These

combination formulations may contain first and/or second-generation pyrethroids or a variety of combinations

of a one or more pyrethroids or organophosphates. Many first and second-generation pyrethroid products

contain a synergist (i.e. piperonyl butoxide and MGK 264), which increases the insecticidal activity of the

product.

The second-generation pyrethroids are the most common insecticides used in urban pest control. Their frequent

use in structural pest control is largely attributed to their exceptional insecticidal activity and greatly reduced

rates of application. Some second-generation pyrethroids are used singly or in combination with other

pyrethroids or organophosphates. Some of the common second generation insecticides currently used around

schools, either singly or in combination with other insecticides, include: cypermethrin (Demon), permethrin

(many), cyfluthrin (Tempo), and lamda-cyhalothrin (Commodore). The signal word of first and second-

generation pyrethroid insecticide products varies with the active ingredient and the formulation. A primary

factor related to their toxicity is the degree of eye irritation caused by the active ingredient concentrate.

FLUORINATED HYDROCARBONS

This broad classification is applied to two relatively new

insecticide classes: amidinohydrazones and fluoroaliphatic

sulfones, both contain fluorine in their chemical structure.

The amidinohydrazones include several insecticide products

(Maxforce bait products) containing the active ingredient

hydramethylnon. Hydramethylnon is primarily used in baits to

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control ants and cockroaches. It functions as a slow acting stomach poison. It is available in a number of

formulations including gels for crack and crevice treatments of cockroaches and in tamper-resistant bait stations

for control of ants and cockroaches. Bait formulations containing hydramethylnon have low toxicity to

mammals and are readily accepted by insects. The most important factor determining their effectiveness is

proper bait placement. Schools choosing to use these products should seek the advice of a professional pest

control specialist or other knowledgeable persons before using them.

Like the amidohydrazones, the fluoroaliphatic sulfones include one active pesticide ingredient, sulfluramid

(Dual Choice products). Sulfluramid, like hydramethylnon is a relatively non-toxic ingredient used in

prepackaged consumer bait products for control of cockroaches and ants. Like hydramethylnon, sulfluramid

kills insects by interfering with a specific metabolic process.

BIOLOGICAL PESTICIDES

This group contains the microbial pesticides, insect growth regulators, pheromones and the botanical pesticides.

Except for the botanicals, this group differs from other pesticides groups in that they consist of a variety of

chemicals of natural origin or synthetic versions of natural chemicals that target specific species and usually

have little impact on non-targeted species. The botanicals pesticides are extracted from plants and are used

alone or with other pesticides. They usually are used to control a wide variety of insect or weed pests.

Biological pesticides that are sometimes used or potentially could be used around schools include microbial

pesticides, insect growth regulators, pheromones and select botanicals, such as pyrethrum and corn gluten.

Microbial Pesticides

An increasing number of pathogens (bacteria, fungi, viruses) are being registered as pesticides for control of

specific insects and plant diseases, especially in agriculture. Currently, only one pathogen, a naturally occurring

fungus, has been registered for use in structural pest control. The fungus, Metarhizium anislopia, is available as

Biopath and is used in tamper-resistant chambers as a slow acting contact poison for controlling cockroaches.

The spores of a number of varieties of the bacteria, Bacillus thuringiensis, are available in a number of

commercial products for controlling larval mosquitoes, caterpillars and other select species of insects. These

species specific and low toxicity pesticide products have some potential use for controlling larval mosquitoes in

school yards or for controlling caterpillar pests in school gardens or greenhouses.

Avermectins

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Avermectins and abamectin are synonymous for a mixture of two chemicals produced in a fermentation process

by the soil-inhabiting fungus, Streptomyces avermitilis. For convenience, the mixture of these two chemicals is

referred to as “avermectins”. They kill insects by stimulating the production of a substance in the insect that

blocks nerve signals and causes death by paralysis. Avermetins are available as a dry flowable bait formulation

that is applied to cracks and crevices indoors and outdoors to control cockroaches. One draw back of this

pesticide is that it is not labeled for use in food preparation areas.

Insect Growth Regulators (IGR’s)

Insect growth regulators are a group of compounds that affect the ability of insects to grow and mature

normally. They consist of synthetic chemicals that mimic the naturally occurring growth hormones that occur

within an insect’s body. There are two classes of materials that currently fall into the IGR category; juvenile

hormone analogs (juvenoids) and chitin synthesis inhibitors. Currently, juvenoids are the only IGR’s available

for use by professional pest management for school pest situations. The effects on the insect vary with the

chemical nature of the IGR. Some extend the period of larval or nymphal stages of insects, others prohibit the

larval stage from pupating or its ability to pupate, and other IGR’s cause infertile adults. IGR’s are effective at

very low rates and present a very low risk to humans and pets. However, they are effective on very limited

number of pests and typically take several months to affect a pest population.

Three IGR compounds are formulated into urban IGR pesticide products: fenoxycarb, hydroprene and

methoprene. Fenoxycarb (Torus and Award) can kill some early nymphal instars of insects such as fleas and

cockroaches. It can prevent their nymphs from becoming adults and it can also reduce egg hatch in treated

females. Hydroprene (Gencor, Gentrol) is used on cockroaches. Treated nymphs develop into infertile adults.

Hydroprene is often initially applied as mixture of hyrdroprene and a conventional insecticide to control

existing adult cockroaches that are not affected by hydroprene alone. Methoprene spray is used against fleas

(Precor) and pharaoh ants (Pharorid). It prolongs larval development and prevents pupation in fleas and

prevents the larvae of pharaoh ants from developing normally and causes the queen to be sterile. Methoprene

baits often take several months to eliminate a colony of pharaoh ants.

Chitin synthesis inhibitors disrupt the normal molting process of insects by interfering with chitin, a major

component of an insect’s exoskeleton. Currently one compound, hexaflumuron (Sentricon) show considerable

promise against certain termite species. Other similar bait products are currently under development for control

of a variety of structural pests.

Pheromones

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Insects release chemical substances into the air that convey information to and produce specific responses in

other individuals of the same species. These chemicals are called pheromones. Synthetic pheromones are used

to assist in insect trapping or monitoring programs. These pheromones cause certain insects (ants, moths and

beetles) to gather by mimicking signals that promote aggregation, either for mating or food or both. Pheromones

are often included as a component of sticky traps that are one of the primary tools used in structural insect

monitoring programs.

Botanicals

Examples of botanical pesticides include pyrethrum, rotonone, nicotine, strychnine, and corn gluten. The fact

that these compounds are “natural” does not mean that they have low toxicity. Nicotine containing insecticides

and strychnine containing rodenticides are very toxic to humans and animals and EPA

has suspended many of their uses.

Pyrethrum insecticides are best known for their rapid knockdown properties and low

residual activity. Pyrethrum also has a good safety record in consumer and commercial

pest control products. However, one key disadvantage is that they are toxic to fish and

can cause skin irritation in humans.

Corn gluten is the protein and nitrogen residue remaining after starch is removed from

corn kernels during wet-milling. It has recently been found to have preemergent

herbicide properties that can prevent the germination of certain annual weed seeds.

Corn gluten has recently been gaining some acceptance as a natural herbicide in golf course and residential turf

management.

“Pesticide” is an all-inclusive word used to designate anything that kills pests such as insects (insecticide),

fungus (fungicide), mites (miticide), weeds (herbicide), slugs and snails (molluscicides), nematodes

(nematicides) and bacteria (bactericides).

For centuries, ever since man moved from a nomadic existence to a hunter-gatherer then to an agrarian society,

farmers and home vegetable gardeners bemoaned the fact that many insects devoured their crops, often leading

to starvation and eventual death of loved ones because of the loss.

USING PESTICIDES WISELY

Toxicity Categories of Pesticides and Signal Indicators:

Category Signal Mammalian Oral LD500 Dermal LD50 Inhalation LC50

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Toxicity (mg/kg) (mg/kg) (mg/L)

I

Danger

Poison

Skull

High 0-50 0-200 0-2000

II Warning Moderate 51-500 201-2,000 2,001-20,000

III Caution Low >500 >2,000 >20,000

Insects and diseases may develop a resistance to many pesticides, both organic and inorganic. Gardeners may

find it necessary to switch to different pesticides if insect or fungal populations do not seem to be affected or

lowered by the poisons used.

Carefully read the directions and precautions twice before using pesticides. Use all protective gear

recommended on the label.

Use all pesticides sparingly and wisely. When inorganic pesticides first came on the market, gardeners would

spray the landscape “fence to fence” unaware of the consequences of their actions. Spray only the target insect

or fungus or plant.

Some pesticides are toxic to birds, bees, fish and some mammals. The label will tell you if it is. If using

homemade pesticides, be aware of potential harm.

Sadly, insecticides do not distinguish between the “good guys” and the “bad guys” and all too often we

eradicate the beneficial or harmless insects when using an insecticide.

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