Types of Pesticides
Pesticides are often referred to according to the type of pest they control. Another way to think about pesticides is to consider those that are chemical pesticides or are derived from a common source or production method. Other categories include biopesticides, antimicrobials, and pest control devices.
Some examples of chemically-related pesticides follow. Other examples are available in sources such as Recognition and Management of Pesticide Poisonings.
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).
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.
Pesticides that are related because they address the same type of pests include:
- 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 Antimicrobials
- Kill microorganisms (such as bacteria and viruses).
- 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.)
- Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals.
- Kill microorganisms.
- Disinfectants and sanitizers
- Kill or inactivate disease-producing microorganisms on inanimate objects.
- Kill fungi (including blights, mildews, molds, and rusts).
- Produce gas or vapor intended to destroy pests in buildings or soil.
- Kill weeds and other plants that grow where they are not wanted.
- 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.
- Kill snails and slugs.
- Kill nematodes (microscopic, worm-like organisms that feed on plant roots).
- Kill eggs of insects and mites.
- Biochemicals used to disrupt the mating behavior of insects.
- Repel pests, including insects (such as mosquitoes) and birds.
- Control mice and other rodents.
The term pesticide also includes these substances:
- Cause leaves or other foliage to drop from a plant, usually to facilitate harvest.
- 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.
What about pest control devices? EPA also has a role in regulating devices used to control pests. More specifically, a "device" is any instrument or contrivance (other than a firearm) intended for trapping, destroying, repelling, or mitigating any pest. A mousetrap is an example of a device. 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.
For more information on devices, see Pest Control Devices.