A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, rodenticides, molluscicides and various other substances used to control pests. Under United States federal law, any substance or mixture of substances intended for use as a plant regulator, defoliant or desiccant is also considered a pesticide.

caption Boll weevil on a cotton boll. (Source: USDA; Credit: Rob Flynn).

Pests are living organisms that occur where they are not wanted or that cause damage to crops or humans or other animals. Examples include:

Many household products are pesticides. All of these common products are considered pesticides:

  • Cockroach sprays and baits;
  • Insect repellents for personal use;
  • Rat and other rodent poisons;
  • Flea and tick sprays, powders, and pet collars;
  • Kitchen, laundry, and bath disinfectants and sanitizers;
  • Products that kill mold and mildew;
  • Some lawn and garden products, such as weed killers; and
  • Some swimming pool chemicals.

Types of Pesticides

  • Algicides -  Control algae in lakes, canals, swimming pools, water tanks, and other sites.
  • Antifouling agents - Kill or repel organisms that attach to underwater surfaces, such as boat bottoms.
  • Antimicrobials - Kill microorganisms (such as bacteria and viruses).
  • Attractants - Attract pests (for example, to lure an insect or rodent to a trap). (However, food is not considered a pesticide when used as an attractant.)
  • Biocides - Kill microorganisms.
  • Disinfectants and sanitizers -  Kill or inactivate disease-producing microorganisms on inanimate objects.
  • Fungicides - Kill fungi (including blights, mildews, molds, and rusts).
  • Fumigants -  Produce gas or vapor intended to destroy pests in buildings or soil.
  • Herbicides -  Kill weeds and other plants that grow where they are not wanted.
  • Insecticides - Kill insects and other arthropods.
  • Miticides (also called acaricides) - Kill mites that feed on plants and animals.
  • Microbial pesticides - Microorganisms that kill, inhibit, or out compete pests, including insects or other microorganisms.
  • Molluscicides - Kill snails and slugs.
  • Nematicides - Kill nematodes (microscopic, worm-like organisms that feed on plant roots).
  • Ovicides - Kill eggs of insects and mites.
  • Pheromones - Biochemicals used to disrupt the mating behavior of insects.
  • Repellents - Repel pests, including insects (such as mosquitoes) and birds.
  • Rodenticides - Control mice and other rodents.

The term pesticide also includes these substances:

  • Defoliants - Cause leaves or other foliage to drop from a plant, usually to facilitate harvest.
  • Desiccants - Promote drying of living tissues, such as unwanted plant tops.
  • Insect growth regulators - Disrupt the molting, maturity from pupal stage to adult, or other life processes of insects.
  • Plant growth regulators - Substances (excluding fertilizers or other plant nutrients) that alter the expected growth, flowering, or reproduction rate of plants.

Chemical Pesticides

Some examples of chemically-related pesticides are

  • Organophosphate Pesticides - These pesticides affect the nervous system by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. Most organophosphates are insecticides. They were developed during the early 19th century, but their effects on insects, which are similar to their effects on humans, were discovered in 1932. Some are very poisonous (they were used in World War II as nerve agents). However, they usually are not persistent in the environment.
  • Carbamate Pesticides affect the nervous system by disupting an enzyme that regulates acetylcholine, a neurotransmitter. The enzyme effects are usually reversible. There are several subgroups within the carbamates.
  • Organochlorine Insecticides were commonly used in the past, but many have been removed from the market due to their health and environmental effects and their persistence (e.g. DDT and chlordane). (see Chlorinated pesticides)  
  • Pyrethroid Pesticides were developed as a synthetic version of the naturally occurring pesticide pyrethrin, which is found in chrysanthemums. They have been modified to increase their stability in the environment. Some synthetic pyrethroids are toxic to the nervous system.


Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides. At the end of 2001, there were approximately 195 registered biopesticide active ingredients and 780 products. Biopesticides fall into three major classes:

  1. Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides can control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest[s]. For example, there are fungi that control certain weeds, and other fungi that kill specific insects.

    The most widely used microbial pesticides are subspecies and strains of Bacillus thuringiensis, or Bt. Each strain of this bacterium produces a different mix of proteins, and specifically kills one or a few related species of insect larvae. While some Bt's control moth larvae found on plants, other Bt's are specific for larvae of flies and mosquitoes. The target insect species are determined by whether the particular Bt produces a protein that can bind to a larval gut receptor, thereby causing the insect larvae to starve
  2. Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant. For example, scientists can take the gene for the Bt pesticidal protein, and introduce the gene into the plant's own genetic material. Then the plant, instead of the Bt bacterium, manufactures the substance that destroys the pest. The protein and its genetic material, but not the plant itself, are regulated by EPA.
  3. Biochemical pesticides are naturally occurring substances that control pests by non-toxic mechanisms. Conventional pesticides, by contrast, are generally synthetic materials that directly kill or inactivate the pest. Biochemical pesticides include substances, such as insect sex pheromones, that interfere with mating, as well as various scented plant extracts that attract insect pests to traps. Because it is sometimes difficult to determine whether a substance meets the criteria for classification as a biochemical pesticide, EPA has established a special committee to make such decisions.


A pest control "device" is any instrument or contrivance (other than a firearm) intended for trapping, destroying, repelling, or mitigating any pest. Although pest control devices are not required to be registered with EPA, some other regulatory requirements do apply. Some common examples of such pest control devices that are subject to the other regulatory requirements are:

  • Ultraviolet light systems, certain water and air filters, or ultrasonic devices that make claims that the device kills, inactivates, entraps, or suppresses growth of fungi, bacteria, or viruses in various sites;
  • High frequency sound generators, carbide cannons, foils, and rotating devices that make claims about repelling pests, such as birds and mice.
  • Black-light traps, fly traps (without an attractant substance other than food), electronic and heat screens, fly ribbons, glueboards and fly paper that make claims about killing or entrapping insects; and
  • Mole thumpers, sound repellants, foils and rotating devices that make claims about repelling certain mammals.

For more information on devices, see Pest Control Devices.

Risks and benefits of pesticides

By their very nature, most pesticides create some risk of harm. Pesticides can cause harm to humans, animals, or the environment because they are designed to kill or otherwise adversely affect living organisms.At the same time, pesticides are useful to society. Pesticides can kill potential disease-causing organisms and control insects, weeds, and other pests.

Biologically-based pesticides, such as pheromones and microbial pesticides, are becoming increasingly popular and often are safer than traditional chemical pesticides. In addition, EPA is registering reduced-risk conventional pesticides in increasing numbers.

Regulation of pesticides

In the United States, pesticides are regulated by the U.S. Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). In addition, under FIFRA, a substance used as a plant regulator, defoliant, or desiccant is defined as a pesticide and regulated accordingly. All pesticides must be registered and carry a label approved by EPA.

The U.S. definition of pesticides is quite broad, but it does have some exclusions:

  • Drugs used to control diseases of humans or animals (such as livestock and pets) are not considered pesticides; such drugs are regulated by the Food and Drug Administration.
  • Fertilizers, nutrients, and other substances used to promote plant survival and health are not considered plant growth regulators and thus are not pesticides.
  • Biological control agents, except for certain microorganisms, are exempted from regulation by EPA. (Biological control agents include beneficial predators such as birds or ladybugs that eat insect pests.)
  • Products which contain certain low-risk ingredients, such as garlic and mint oil, have been exempted from Federal registration requirements, although State regulatory requirements may still apply. For a list of ingredients which may be exempt, and a discussion of allowable label claims for such products, see EPA's Pesticide Registration Notice 2000-6, "Minimum Risk Pesticides Exempted under FIFRA Section 25(b)" (33 KB, PDF).

Unlike pesticides, EPA does not require devices to be registered with the Agency. Devices are subject to certain labeling, packaging, record keeping, and import/export requirements, however. In addition, the establishment where a device is produced must be registered with EPA who will assign an Establishment Number.

Further Reading




Agriculture, U. (2013). Pesticide. Retrieved from