Many of the words defined here have additional meanings. The definitions given here are related to pests, pesticides, and pest management.


Absorption — Movement of a chemical into a plant, animal, or the soil. Plants absorb substances through leaves, stems, or roots, animals absorb substances through skin breathing organs, stomach, mouth or intestines. Compare to adsorption.

Acaricide — A pesticide used to control mites and ticks. The term refers to Acarina (or Acari), the taxonomic group which mites and ticks belong.

Active ingredient — The component of a pesticide formulation that kills or controls pests. In other words, the chemical that is responsible for the toxic effect in a formulation.

Acute — In regard to pesticides, refers to effects from one exposure or exposure for a short period.

Acute dermal toxicity— The toxicity of a single dose (or short exposure) of a pesticide when absorbed through the skin.

Acute inhalation toxicity — The toxicity of a single dose (or short exposure) of a pesticide when inhaled into the lungs.

Acute oral toxicity— The toxicity of a single dose (or short exposure) of a pesticide when taken by mouth (eaten, swallowed, licked, etc.).

Additive — Any substance added to a pesticide to improve its performance. Same as adjuvant.

Adjuvant — An ingredient added to a pesticide to modify or enhance the effectiveness of the active ingredient

Adsorption — The process by which a substance is held (bound) to the surface of a soil particle or mineral in such a way that the substance is available only slowly. Clay and highly organic soils have a tendency to adsorb pesticides. Compare to absorption.

Adult — A full-grown, sexually mature insect, mite or other animal or plant.

Aerosol — A low-concentrate solution of a pesticide or combination of pesticides, usually in an oil solution formulated especially for use in aerosol generators.

Agitator — A paddle (or other mechanical device), air, or hydraulic action used to keep a pesticide formulation mixed in the tank.

Air blast — A type of pesticide sprayer that can deliver high and low volumes of spray; used for orchards, shade trees, sprayer vegetables, and fly control.

Annual — A plant that grows from a seed, produces flowers, fruit or seed the same year, and then dies.

Anticoagulant — A chemical that interferes with the normal clotting of blood. Some rodenticides are based on this principle.

Antidote — A medicine or other remedy for counteracting the effect of a poison. Antidotes are effective in reversing effects caused by certain pesticides, if administered promptly.

Applicator — A person or piece of equipment which applies pesticides.

Aquatic weeds — Plants or weeds that grow in water. The plants may float on the surface, grow up from plants or the bottom of the body of water (emergent), or grow under the surface of the water (submergent).

Artificial respiration — A form of first aid given to a person who has stopped breathing in order to get the person breathing again.

Atomize — To break up a liquid into very fine droplets by forcing it through a nozzle-like device having a very small opening.

Attractants — Substances or devices that attract insects or other pests to areas where they can be trapped or killed.

Avicide — A pesticide used to control birds.


Bacteria — Single-celled microorganisms (germs), some of which cause diseases in plants or animals. They cannot be seen without a microscope. (Singular: bacterium)

Bait — A food or other material that will attract a pest to a pesticide or to a trap where it will be trapped or killed. Baits can be mixed with pesticides in certain situations.

Bait shyness — The tendency for rodents, birds, or other pests to avoid a poisoned bait.

Biennial plant — A plant with a 2-year life cycle. It produces leaves and stores food in the first year, then produces fruits and seeds in the second year. After the second year the plant dies.

Biochemical — Having to do with the chemistry of living things.

Biological control (BC) — The use of colonized or naturally occurring parasites or predators to control pest populations. Some would expand the definition to include pathogenic microorganisms, since they are also parasites.

Biopesticides — See biorational pesticides

Biorational pesticides — Pesticides derived from natural materials as animals, plants, bacteria, and certain minerals. EPA recognizes three categories of biorational pesticides: (1) microbial pesticides, (2) plant incorporated-protectants, and (3) biochemical pesticides. Biorational pesticides are subject to FIFRA regulation. Most biological control agents are not.

Boom — A section of pipe (or tubing) to which pesticide sprayer nozzles can be attached to increase the area that can be treated by a pesticide in a single pass of a vehicle.

Botanical pesticides – Pesticides made from plants. Examples: nicotine, pyrethrum, rotenone and strychnine.

Broadcast application — A uniform application over an entire area.

Broadleaf plants — Plants having wide, rounded, or flattened leaves and netted veins. Examples: dandelions and roses. Compare to Narrow leaf plants.

Broad spectrum pesticide — A pesticide that is toxic to a wide range of pests. Same as Non-selective.

Buildup — Accumulation of a pesticide in soil, animals, or in the food chain.


Calibration — The measurement and adjustment of pesticide application equipment to apply a pesticide formulation at a desired application rate.

Canister — A metal or plastic container filled with absorbent materials that filter fumes and vapors from the air before they are inhaled by an applicator.

Carbamate — A synthetic organic pesticide that belong to a group of chemicals that are salts or esters of carbonic acid. Carbamates are used as fungicides, herbicides, and insecticides. Examples: aldicarb, carbaryl, carbofuran, and methomyl.

Carcinogen — A substance or agent capable of producing cancers.

Carcinogenicity — The capability of a substance to cause cancers.

Carrier — An adjuvant which is added to (or which dilutes) the active ingredient so that the formulation becomes easier to apply. Petroleum solvents and talc are examples. Also, the material that carries the pesticide to target. Water in a hydraulic sprayer or air in a mist blower are examples of this.

Cartridge — The part of the respirator that absorbs fumes and vapors from the air before the applicator inhales them.

Caution – The signal word used on pesticide labels to indicate a Toxicity Category III product.

Certified applicator— An individual who is certified to use or supervise the use of a restricted pesticide.

Cholinesterase – An enzyme found in the bodies of animals that controls nerve impulses. It is necessary for proper nerve function. Its activity can be affected in insects and warm-blooded animals (including people) by organophosphates and carbamates.

Compatibility — The degree to which two or more pesticides can be combined without significant reduction in effectiveness or safety.

Complete metamorphosis — The process of insect development which includes the egg, larva, pupa, and adult stages.

Controls — Experimental subjects not treated with a test chemical. An experiment that does not use controls is called "uncontrolled" and the results derived are usually not taken seriously by others.

Corrosive poison — A type of poison that contains a strong acid or base which will severely burn the skin, mouth, stomach, or other organs.

Cross contamination — When one pesticide gets into or mixes with another pesticide accidentally. This usually occurs in a previously-used pesticide container or in a poorly cleaned sprayer.


Danger – The signal word used on pesticide labels to indicate a highly toxic pesticide (Toxicity Category I). This signal word may be accompanied by the word Poison and the skull and crossbones symbol.

Decontaminate — To make safe, purify, make fit for use again by removing any pesticide from equipment or other surfaces as directed by a pesticide label, an agricultural authority, or the manufacturer of the pesticide.

Defoliant — A pesticide which causes the leaves of a plant to drop off.

Degradation — The breakdown of a more complex chemical into a less complex form. This process can be a result of the action of microbes, water, air, sunlight, or other agents.

Delayed action — The lack of an immediate response by a plant to an application of an herbicide. With some herbicides a delayed response is expected and it may take a while for maximum effects to be observed. Usually treated plants stop developing soon after treatment and then gradually die.

Deposit — The amount of pesticide remaining on the target immediately following an application. Compare to Residue.

Dermal — Through or by the skin; of or pertaining to the skin.

Dermal toxicity — The toxicity of a pesticide when it comes in contact with and absorbed through the skin. Dermal toxicity is the greatest hazard to people handling pesticides.

Desiccant — A pesticide used to draw moisture from or dry up a plant, plant part, or insect. Desiccants are used primarily for pre-harvest drying of actively growing plant tissues when seed or other plant parts are developed but only partially mature; or for drying of plants which normally do not shed their leaves, such as rice, corn, small grains, and cereals.

Diluent — Material, usually oil or water, mixed with a concentrate to dilute it to field strength.

Dilute — (verb) To make a pesticide less concentrated by adding water, oil, or other liquid or solid.

Dose (dosage) — The application rate of a pesticide, usually expressed in units of weight per unit of area, such as pounds per acre. Also, a measure used in testing to determine acute and chronic toxicities. In this case, usually expressed in units of weight of a chemical per unit of weight of a test animal or human, such as milligrams per kilogram (mg/kg).

Drift — The movement of pesticide droplets or particles by wind and air currents from the target area to an area not intended to be treated.

Dust (D) — A finely ground dry mixture combining a small amount of pesticide with an inert carrier such as clay, talc, or volcanic ash.


Ecology — The study of the relationship between a plant or animal and its surroundings.

Effective Dose (ED) — The ED50 is the dose that is effective in killing or otherwise affecting 50 percent of the tested subjects.

Emulsifiable concentrate (EC or E) – An oil solution containing a high concentration of active ingredient and an emulsifying agent. The emulsifying agent aids in mixing the concentrate with water to produce an emulsion for spraying.

Emulsifier — A chemical that helps one liquid form tiny droplets and thus remain (emulsifying suspended in another liquid.

Emulsion — A mixture in which one liquid is suspended (mixed up) as tiny droplets in another liquid. Example: oil in water.

Encapsulation — A method of formulating pesticides, in which the active ingredient is encased in a material (often plastic), resulting in sustained pesticidal release and decreased hazard. Also, a method of disposal of pesticides and pesticide containers by sealing them in sturdy, waterproof, chemical-proof containers which are then sealed in thick plastic, steel, or concrete to resist damage of breakage so the contents cannot escape to the environment.

EPA — The US Environmental Protection Agency, the federal agency responsible for the protection of the environment in the United States.

Epidemiological — Having to do with the study of the incidence and distribution of diseases in the broad sense (to include infectious diseases, metabolic disorders, poisonings, genetic defects, allergies, etc.).

Evaporate — To form a gas and disappear into the air; to vaporize.

Exemption — An exception to a policy, rule, regulation, law, or standard.

Exoskeleton — The segmented external skeleton of an arthropod.

Exposure — Contact with a pesticide through skin (dermal), mouth (oral), lungs (inhalation/respiratory), or eyes.


Face shield — A transparent piece of protective equipment used by a pesticide applicator to protect the face from exposure.

FDA – The US Food and Drug Administration, the federal agency that monitors pesticide residues on food products.

FIFRA — The Federal Insecticide, Fungicide, and Rodenticide Act, the federal law pertaining to pesticide regulation and use in the USA. The original act was enacted in 1947. It has been amended many times since then.

First aid — The first effort to help a victim while medical help in on the way.

Flowable (F) — Very finely ground solid material which is suspended in a liquid; usually contains a high concentration or large amount of the active ingredient and must be mixed with water when applied.

Fogger — An aerosol generator; a type of pesticide spray equipment that breaks pesticides into very fine droplets (aerosols or smokes) and blows or drifts the "fog" onto the target area.

Foliage — The leaves, needles, stems, and blades of plants and grasses.

Foliar application — Spraying a pesticide onto the stems, leaves, needles, and blades of grasses, plants, shrubs, or trees.

.Formulation — The resulting mixture of pesticide active ingredients, diluents, synergists, additives, and carriers. This is the form that pesticides are sold by distributors or retailers. It is also the form of pesticides that EPA registers.

Fume — A smoke, vapor, or gas.

Fumigant — A pesticide that enters the pest in the form of a gas and kills it. The fumigant may be a liquid that changes to a gas when it is applied. Methyl bromide, phostoxin, chloropicrin, and carbon bisulfide are examples.

Fungi — Groups of small plant organisms (often microscopic) which cause rots, molds, and plant diseases. Fungi grow from seed-like spores and produce tiny thread-like growths. Molds, mushrooms, and yeasts are examples. (Singular: fungus).

Fungicide — A pesticide used to control fungi.


Gas mask — A type of respirator which covers the entire face and protects the eyes as well as the nose and mouth. It filters and cleans the air better than cartridge respirators and is less likely to leak around the edges. This device is effective against air which contains sprays, dusts, or gases. (Note: A simple respirator will protect against a spray or dust without covering the eyes, but not against poisonous gases.)

Gram — A metric weight measurement equal to 1/l,000th of a kilogram; approximately 28.5 grams equal one ounce.

Granular pesticide (G) – A pesticide in the form of pellets, all of which are larger than dust particles. A granular formulation is dry and ready-to-use, and is made of small amount of pesticide and an inert carrier; the active ingredient is mixed with, absorbed, adsorbed, or pressed on or into the inert carrier.

Growth regulator — A pesticide that interferes with the normal growth or reproduction of a plant or animal. Growth regulators are considered biorational pesticides.


Hazard — A danger or risk of injury or other harm faced in connection with exposure to a pesticide. The degree of hazard is a result of a combination of toxicity and exposure.

Hectare — A metric area measurement equal to 10,000 square meters or approximately 2.47 acres.

Herbicide — A pesticide used to control plants, especially weeds.

High pressure sprayer — Same as Hydraulic sprayer.

Hormones — Chemicals naturally present in plants or animals that control growth or other physiological processes. Hormone-like chemicals can be synthesized to regulate plant and animal growth. They can also be used as pesticides through disruption of growth processes. Both naturally-occurring and synthesized chemicals that are used as pesticides are considered biorational.

Host — A living plant or animal that a pest depends on for survival.

Hydraulic sprayer — A machine that delivers large volumes of pesticide spray at high pressures (up to several hundred pounds per square inch) to the target. Hydraulic sprayers are used primarily for fruit trees, shade trees, and ornamentals. Same as High pressure sprayer.

Hydrocarbon — A chemical whose molecules consist entirely of carbon and hydrogen atoms. Crude oil is a mixture largely of hydrocarbons. Methane (natural gas) is the simplest hydrocarbon, with each molecule containing one atom of carbon and four atoms of hydrogen.

Hydrogen ion — A general term for all ions of hydrogen and its isotopes. The concentration of hydrogen ions in a solution is a measure of acidity or alkalinity, and is expressed in terms of the pH of the solution. See pH.


IGR — Insect growth regulator.

Impermeable — Characteristic of a living or non-living structure that cannot be penetrated by gases or liquids. The term is often applied to membranes of various types. A semipermeable membrane would be one that is only partially permeable, and some substances can pass through but others cannot.

Inactive — Status of a substance that does not react chemically with any other substance.

Incompatible — Refers to two or more pesticides that cannot be mixed together without a loss of effectiveness of one or both of the pesticides. Incompatible pesticides also my cause unintended injury to plants or animals.

Infestation —Pests that are found in an area or location where they are not wanted.

Ingest —To eat, drink, and swallow a substance.

Inhalation —The process of taking air into the lungs; breathing in.

Inhalation toxicity — The toxicity of a pesticide when breathed in through the lungs.

Inhibitor —A pesticide used to prevent or suppress growth or other physiological processes in plants. Also called a "growth inhibitor". See Growth regulator.

InjectTo force a pesticide into a plant, animal, building, other structure, or the soil.

Inorganic pesticides — Pesticides which do not contain carbon. Examples: Bordeaux mixture, copper sulfate, sodium arsenite, sulfuric acid, and salt.

Insect —A small invertebrate animal with three body regions and six jointed legs; may have two, four, or no wings.

Insecticide —A pesticide used to control insects.

Integrated pest management (IPM) — The management of pest problems using a combination of ecologically-sound approaches.

Interval — The time between two pesticide applications. Also, the time period between the final pesticide application and harvest.

Invertebrate — The very large group of animals that lack backbones. Insects, jellyfish, starfish, shellfish, squid, and spiders are examples.

IR-4 – Acronym for USDA Interregional Program 4, a program for the cooperative registration of minor uses of pesticides.


Kg — Kilogram. A metric weight measurement equal to 1,000 grams or approximately 2.2 pounds.


Label — Technical information about a pesticide in the form of printed material attached to or printed on the pesticide container.

Labeling — Technical information about the pesticide in the form of printed material provided by the manufacturer or its agent, including the label, flyers, handouts, leaflets, and brochures.

Larvae — Immature forms of invertebrate organisms. In insects, the forms that appear after hatching from eggs and before becoming a pupae.

Larvicide — A pesticide used to kill larvae, usually of insects.

LC50 The median lethal concentration of an active ingredient of a pesticide, i.e., the concentration of an active ingredient at which 50% of a group of test animals will die. LC50 is usually used to describe toxicity of pesticides in the air as gasses, dusts, or mists. LC50 is ordinarily expressed as parts per million (ppm) when the material is a gas, and micrograms per liter (mg/l) when a dust or mist. It is often used as the measure of Acute inhalation toxicity. As with all such indicators of toxicity, the lower the value, the more poisonous the pesticide.

LD50 The median lethal dose of an active ingredient of a pesticide, i.e., the dose of an active ingredient at which 50% of a group of test animals will die. LD50 is usually used to describe toxicity of pesticides in liquid form. Toxicity generally is expressed in milligrams of pesticide per kilogram of body weight (mg/kg). It is often used to measure Acute oral toxicity or Acute dermal toxicity. As with all such indicators of toxicity, the lower the value, the more poisonous the pesticide.

Leaching — The movement of a substance downward or out of the soil as the result of water movement.

Legal residue — A residue on a food crop for which a pesticide tolerance has been established and that is less than the permitted level.

Lethal — Causing or capable of causing death.

Life cycle — The procession of stages in the life development of an organism.

Liter — A metric measurement of volume equal to one cubic decimeter or, when dealing with liquid measurement, a little more than one quart.

Low concentrate solution (S) — A solution that contains a low concentration of active ingredient in a highly refined oil. These solutions are usually purchased as stock sprays and space prays and for use in aerosol generators.

Low pressure boom sprayer — A machine that delivers low to moderate volumes of pesticide at pressures of 30–60 psi. These sprayers most often are used for field and forage crops, pastures, and rights-of-way. Compare to hydraulic sprayer.

Low volume air sprayer — A machine similar to an Air blast sprayer, but with somewhat lower water volume and higher air velocity. This combination produces extremely fine droplets. Same as Mist blower.

Low volume spray — A spray application of 5–20 gallons per acre.


Mammals — Warm-blooded animals that nourish their young with milk and have skin that is more or less covered with hair.

Mechanical agitation — The stirring, paddling, or swirling action of a device which keeps a pesticide and any additives mixed in a spray tank.

Metabolism — The sum of the physical and biological processes in an organism by which chemicals are usually converted to energy and heat.

Metamorphosis — Changes in the shape, form, structure, and size of insects during their life cycle.

Metric — A system of measurement used by most of the world. The USA is one of the few nations in the world not to have adopted the metric system completely. Meters, grams, and liters are examples of metric units of measure.

Milligram (mg). A metric weight measurement equal to 1/1,000th of a gram; approximately 28,500 mg equal one ounce.

Milligrams per kilogram (mg/kg) — A measurement used to express the number of kg of a pesticide per kg of body weight of a test animal that will produce some kind of effect. The effect can be a sign of irritation, evidence of illness, or death.

Microbial pesticide — A pesticide consisting of microorganisms or their by-products. Bacillus thuringiensis israelensis (Bti) is an example, and is considered a biorational pesticide.

Microgram — A metric weight measurement equal to 1 millionth of a gram. Approximately 28,500,000 micrograms equal one ounce.

Mist blower — Same as low volume air sprayer.

Mites — Tiny animals closely related to ticks. A mite has six legs during the larval and nymphal stages, but eight legs as adults.

Miticide — A pesticide used to control mites. A miticide is a type of acaricide.

Mode of action — The manner in which a pesticide affects pests, as well as non-target organisms, including people, pets, and other desirable animals.

MPH — Miles per hour.

MTD — Maximum tolerated dose, the highest dose of a chemical that does not alter the life span or severely affect the health of an animal.

Mutagenicity — The ability of a substance to induce a mutation.

Mutation — A change in a gene that is passed from one generation to the next. Such a change may result in a significant change in an organism, or no observable change at all.


Natural enemies — Naturally occurring predators and parasites in the environment that attack pests.

Nematicide — A pesticide used to control nematodes. Nematicides are often applied as a soil fumigants to control nematodes infesting roots of crop plants.

Nematode — A worm-like invertebrate organism that feeds on or in plants and animals. Nematodes have many common names, including roundworms, threadworms, and eelworms. Some are microscope, some are visible to the naked eye, and many kinds are internal parasites of people and other animals.

Neoprene — A synthetic rubber often used to make gloves and boots that offer skin protection against most pesticides.

Neurotoxicity — The poisonous effect of pesticide on nerve tissue.

Nitrophenol — A synthetic organic pesticide that contains carbon, hydrogen, nitrogen, and oxygen.

NOEL — No observable effect level; the dose of a chemical that produces no observable effects when given to animals for long periods of time.

Non-persistent — A pesticide that breaks down almost immediately, or only lasts for a few weeks or less on a treated area. The pesticide may break down by exposure to light, moisture, or microorganisms; or it may evaporate. In some situations, non-toxic break-down products may remain.

Non-selective pesticide — A pesticide that is toxic to a wide range of pests, or toxic to more than one animal or plant. Same as Broad spectrum.

Non-target — Any plant, animal, or other organism that is not the planned object of a pesticide application.

Nozzles — Devices that determine the flow rate, droplet size, and discharge pattern of a pesticide application. Nozzles are mounted in various ways, usually at the ends of wands or along spray booms. Types of nozzles include flat fan, even flat fan, cone, flooding, atomizing, broadcast, and solid stream.

Nymph — The stage of development in certain insects after hatching when the young insect resembles the adult insect but is smaller. In flying insects, nymphs lack fully developed wings.


Oils — Liquids used to carry or dilute an active ingredient in a pesticide formulation. Certain oils may be used alone in aquatic habitats to control mosquito larvae.

Oncogen — A substance capable of inducing tumors. Same as Carcinogen.

Oral — Anything pertaining to the mouth. In pesticide usage, a route of entry of a pesticide when ingested.

Oral toxicity — The toxicity of a pesticide when ingested.

Organic pesticide – Pesticides that contain carbon. The two major types are petroleum oils and synthetic organic pesticides.

Organism — Any living thing.

Organochlorine — Same as Chlorinated hydrocarbon.

Organophosphate — A synthetic organic pesticide that contains carbon, hydrogen, and phosphorous. It acts by inhibiting the blood enzyme cholinesterase. As a rule, organophosphates are less persistent than organochlorine pesticides. Malathion and parathion are organophosphates.

Original container — The package prepared by the manufacturer in which the pesticide is placed and then sold. The package must have a label telling what the pesticide is, how to use it safely and correctly, and how to safely and legally dispose of the empty container.)

Ornamentals — Plants which are used to beautify homes, gardens, and lawns.


Parasite — An organism that lives on, and at the expense of another organism (called the host). The host may be harmed by the parasite, and if the host is a desirable plant or animal the parasite is also a pest. If the host is a pest, the parasite is a biological control agent.

Pathogen — A disease-producing microorganism.

Perennial — A plant that normally lives for more than two years. Shrubs and trees are perennials.

Persistent — A pesticide remains in the environment for a long time.

Pest — An undesirable organism for any one of a variety of reasons. Pests compete with people for food and fiber or attack people, pets, domestic animals, and desirable wildlife directly. Pests can be weeds, insects, rodents, birds, microbial organisms, snails, and many other organisms.

Pesticide — A chemical substance or other agent used to control, destroy, or prevent damage by or protect something from a pest.

Pesticide tolerance — The amount of pesticide residue that may legally remain on a food or feed. The EPA sets pesticide tolerances, and the FDA enforces them.

Petroleum oils — Pesticides refined from crude oil for use as pesticides.

pH — A measurement scale based on the hydrogen ion concentration of a solution used to express its acidity or alkalinity. Pure distilled water has a pH of 7 (=neutral), a solution with a pH less than 7 is acidic, a pH more than 7 is alkaline.

Pheromones — Chemicals produced by insects and other animals to communicate with other members of the same species, or synthetic chemicals that function as pheromones. Some are used as pesticides that act by confusing communication individuals. They are also used as attractants either in surveillance programs or in control programs.

Physiological — Having to do with the mechanisms of body function of organisms.

Phytotoxic — Harmful to plants.

Poison — A chemical or material that can cause injury or death when eaten, absorbed, or inhaled by plants or animals, including people.

Pollutant — A harmful chemical or waste material discharged into the water, soil, or atmosphere; an agent that makes something dirty or impure.

Pollute — To add an unwanted material (often a pesticide) to the environment in a way that degrades it.

Post-emergence — After a specified crop or weed has pushed up through the soil and become visible.

Post-emergent — A pesticide used to control a crop or weed after it has appeared.

Potency — The strength of something. The potency of a pesticide expresses how toxic it is.

Ppb — Parts per billion. Usually describes the amount of a chemical present in soil or water determined by modern analysis.

Ppm — Parts per million. Used in the same way as ppb, but expresses a lower concentration.

Predacide — A pesticide used to control vertebrate predators (usually coyotes).

Predator — An insect or other animal that attacks, feeds on, and destroys other insects or animals. When predators attack pests they are biological control agents. When coyotes attack sheep, they are pests.

Pre-emergence — Before a specified crop or weed has pushed up through the soil and become visible.

Pre-emergent — A pesticide used to control a crop or weed before it has appeared.

Pre-harvest — The time just prior to the picking, cutting, or digging up of a crop.

Pre-plant— The application of a pesticide before planting a crop.

Product — The pesticide as it is packaged and sold; it usually contains an active ingredient plus adjuvants It is

Propellent — A liquid under pressure in self-pressurized pesticides that forces the active ingredient from the container. Upon release into the atmosphere, propellents become gasses.

Properties — The characteristics of a pesticide.

Protectant — A pesticide that is applied before pests are actually found but where they are expected. Sometimes called a preventative.

Protective gear — Clothing, materials, or devices that offer protection from exposure of applicators to pesticides. Gloves, aprons, shoes, coveralls, hats, cartridges, respirators, and gas masks are all examples of protective gear.

Protopam chloride (2-PAM) — An antidote used for organophosphate poisoning, but not for carbamate poisoning.

Psi — Pounds per square inch. A measure of pressure.

Pupa — An insect form that occurs after the final larval stage and before appearance of the adult form in insects having complete metamorphosis (flies, beetles, butterflies and moths, wasps, etc.) Pupae are usually non-feeding, and sometimes immobile (mosquitoes are an exception).

Pyrethrin — The insecticidally-active chemical component of pyrethrum insecticides. Both the active ingredient and the insecticide are sometimes called pyrethrins. The correct usage would be to refer to the former as pyrethrin, the latter as pyrethrum.

Pyrethroids — Synthetic compounds produced for their chemical resemblance and insecticidal similarity to pyrethrin.


Rate — The amount of a pesticide (or pesticide formulation) that is delivered in a pesticide application. Rates are expressed in units of volume or weight per units of area or time (e.g., gallons per acre, pounds per acre, gallons per minute, etc.).

Recommendation — A suggestion from or advice given by a Farm Advisor, Extension Specialist, or other agricultural authority.

Repellent — A pesticide that makes pests leave or avoid a treated area, surface, animal, or plant.

Residual pesticide — A pesticide remaining in the environment for a long time. Some residual pesticides may continue to be effective for days, weeks, and months. The organochlorine dieldrin remained effective as a termite control agent for years.

Residue — The amount of pesticide that remains on or in a crop or animal or on a surface after it has been treated. Residues are usually measured in ppm. Compare to Deposit.

Resistant — Refers to an organism that is able to survive pesticide doses that are fatal to susceptible organisms of the same species..

Respirator — A face mask which filters out poisonous gases and particles from the air, enabling a person to breathe and work safely. Respirators are used to protect the nose, mouth, and lungs from pesticide poisoning.

Respiratory — Having to do with breathing and oxygen uptake.

Respiratory toxicity — The toxicity of a pesticide when inhaled.

Restricted use pesticide — A pesticide that has been classified by the EPA for use only by an appropriately certified applicator.

Reversible — A toxic effect that is temporary or curable.

Rhizome — A root-like underground stem.

Rodent — Any animal of the order Rodentia. Examples include mice, rats, squirrels, gophers, woodchucks.

Rodenticide — A pesticide used to control rodents.

Runoff — The sprayed liquid which does not remain on a plant or sprayed surface. See Point of drip.


Selective pesticide — A type of pesticide that is more toxic to some types of plants or animals than to others. An herbicide that kills crabgrass in a cornfield but does not injure the corn is an example of a selective pesticide.

Sensitive — Easily injured or affected by; susceptible to pesticidal effects at low dosage. Many broadleaved plants are sensitive to 2,4-D.

Sensitive areas — Locations where pesticide applications could cause great harm. Applications in sensitive areas should be done with extreme care and caution. Examples include streams, ponds, houses, barns, parks, etc.

Shock — The severe reaction of the human body to a serious injury. Shock can lead to death if not treated (even if the actual injury was not a fatal one).

Short-term pesticide.— A pesticide that breaks down quickly after application into non-toxic byproducts. Same as Non-persistent.

Signal words — Words which must appear on pesticide labels to indicate the toxicity class to which they belong. Allowable words are Caution, Warning, and Danger-Poison. The skull and cross bones symbol must appear with the signal words Danger-Poison.

Sign — Evidence of exposure to a dangerous pesticide or other disease process in a plant or animal that is observable by a person other than the plant or animal affected. In people, signs are observable by others even if the person affected is unconscious. In other animals and in plants, only signs are available as evidence of poisoning or illness. Compare to Symptom.

Silvicide — A pesticide used to control unwanted brush and trees.

Slurry — A thick suspension of a pesticide made from a wettable powder and water. See Wettable powder.

Soil fumigant — A pesticide in the form of a gas used to control pests in the soil. Some fumigants are in liquid form when applied, but become gasses in the soil. To lengthen the time of effectiveness, covers such as plastic sheets are sometimes used.

Soluble — A characteristic of a material capable of dissolving in a liquid.

Soluble powder (SP) — A dry preparation of finely-ground powder containing a relatively high concentration (15%–95%) of active ingredient that dissolves in water (or another liquid) and forms a solution so that it can be applied.

Solution — The mixture of a substance into another substance (usually a liquid) in which all ingredients are completely dissolved without their chemical characteristics changing. True solutions do not settle out or separate in normal use. Sugar mixed in water is an example of a solution.

Solvent — A liquid that will dissolve another substances to form a solution. When sugar is dissolved in water, the sugar is the solute, the water is the solvent.

Species — A group of populations of potentially interbreeding living organisms. Since passage of the endangered species act, the definition has been broadened to consider a population having some demonstrable stable difference from another population as a species in the legal sense, even if the populations are potentially interbreeding.

Spiders – Small to moderately large animals classified in the Class Arachnida. Spiders are closely related to mites and ticks, and along with insects are classified as arthropods.

Spillage — Any escape, leakage, dripping, or running over of a pesticide.

Spore — An inactive form of a micro-organism that is capable of becoming active again.

Spot treatment — A pesticide application directed at a small area, such as at specific plants. Opposite of general application. Spot treatments are commonly used in pest control operations in homes and other indoor situations.

Spreader — An adjuvant that increases the area that a given volume of liquid will cover on a solid surface (such as a leaf).

Stomach poison — A pesticide which kills an animal when ingested.

Structural pests — Any animal or organism that can damage houses, barns, and other structures. Examples are termites, carpenter ants, insects and rodents.

Summer annuals — Plants that germinate in the spring, do most of their growing in the summer, produce flowers or seeds, and then die in the fall.

Supplement — Any substance added to a pesticide to improve its performance. Same as Adjuvant.

Surface active agent — An adjuvant that reduces surface tension between two different substances (such as water agent and oil). (Note: Most Adjuvants may be considered surface active agents). Also known as a Surfactant.

Surface water — Water which is located above ground such as ponds, lakes, streams, and rivers.

Surfactant – Same as surface active agent. Surfactants improve the emulsifying, dispersing, spreading, and wetting properties of pesticides.

Susceptibility — The degree to which an organism can be injured or affected by a pesticide at a known dosage.

Susceptible species— A species of organisms that is capable of being injured, diseased, or poisoned by a pesticide; not immune.

Suspension — A pesticide formulation in which finely divided solid particles are mixed in a liquid.

Suspension of a pesticide registration — A preliminary assessment of the risks and benefits of a pesticide prior to cancellation. Suspensions occur when the EPA determines that an imminent hazard is posed by a pesticide. During the suspension process the pesticide in question may be marketed. If the EPA has determined that unreasonable risks would be posed by continued use of the pesticide during the hearing process, an Emergency Suspension Order may be issued. In this case, the pesticide may not be marketed during the hearing process. See also Cancellation.

Swath — The width of ground covered by a sprayer when it moves across a field or other treated area.

Symptom — A feeling of unhealthiness that can be expressed by a person. It may represent a warning of pesticide poisoning. Plants cannot display symptoms, and most animals cannot display them in a readily recognizable form. Reasonable people will disagree on the question of whether non-humans can show symptoms at all, and the word symptom is often misused for "sign".

Synergistic — When the combined action of two or more pesticides is greater than the sum of their activity when used alone.

Synthetic organic pesticides — Man-made pesticides that contain carbon, hydrogen, and other elements.


Target pest — A population of pests at which a pesticide application or other control method is directed.

Toxic dose (TD) — The dose of a chemical that produces signs of toxicity.

Technical grade — A pesticide as it is manufactured by a chemical company before formulation. Commonly used in toxicology laboratories for tests of various kinds.

Thermal — Of, about, or related to heat.

Ticks – Small blood-sucking arthropods belonging to the Class Arachnida (spiders, ticks, and mites). They resemble some insects, to which they are related, but they have eight jointed legs, two body regions, no antennae (feelers), and no wings. As vectors of disease organisms, their importance is second only to mosquitoes.

Tolerance — The legal limit of the amount of pesticide that may remain in or on foods marketed in the USA. Tolerances are established by EPA, and enforced and monitored by FDA..

Toxic — Poisonous to plants and animals, including people.

Toxicant – A Poison; an agent capable of being toxic.

Toxicity — How poisonous a pesticide is to an organism; the innate ability of a pesticide to produce injury. Test animals are used to establish dermal, inhalation, and oral toxicities.

Toxin — A poison produced by a plant or animal.

Trade name — Same as Brand name.

Treated area — A house, barn, field, forest, garden, greenhouse, or other place where a pesticide application has been made.

Tumor — An unregulated growth of cells.


ULV — Ultra low volume. An application of a pesticide at a rate of less than gallon per acre (5 liters per hectare). Because the volumes be sprayed are so small, extremely low doses of insecticide result, even when the pesticides are sprayed undiluted.

Uniform coverage — The even application of a pesticide over an entire area, plant, or animal.

Upwind — A relative location of a person with his or her back towards the direction of a prevailing wind. Also see downwind.

USDA – The US Department of Agriculture.


Vapor — Gas, steam, mist, fog, fume, or smoke.

Vaporize — To evaporate; to form a gas or other forms of vapor.

Vector — A vehicle for transporting a disease-producing organism (pathogen) from one host to another. In vector ecology, the most common vectors are insects and other arthropods. Vectors can transfer pathogens from one animal to another, and from one plant to another.

Vertebrate — An animal with a backbone (bony spinal column) Mammals, fish, birds, snakes, and frogs are vertebrates.

Virus — A microorganism that can grow and reproduce only in living cells of other organisms. Often, viruses cause diseases in their hosts and are then pathogens.

Volatility — How quickly and easily a liquid or solid evaporates at ordinary temperatures when exposed to the air.


Waiting period — Same as Time interval.

Warning – The signal word used on pesticide labels to designate a pesticide that is moderately toxic. (Toxicity Category II).

Weathering — The wearing away of pesticides from the surfaces they were applied to because of wind, rain, snow, ice, and heat.

Weed — A plant growing where it is not wanted.

Weed control — Eradication, inhibition, or limitation of weeds, weed growth, or weed infestations, actions taken to prevent weeds from interfering with crop profitability or the efficiency of other operations.

Wettable powder (WP or W) — A dry (powder) preparation that is mixed with water to form a suspension that is used for spraying. Unlike a Soluble powder, it does not dissolve in water. Suspensions must be added to tanks that have already been partially filled with water, and the mixture must be agitated in some way to avoid lumpy formulations that can clog nozzles and result in improper application.)

Winter annuals — Plants which germinate in the fall or winter, do most of their growing in the spring, produce flower and seeds, and then die by early summer.

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