What is a pesticide?

The term pesticide applies to a number of substances which are used to manage pests such as insects, weeds, fungi, bacteria and viruses.  Pesticides are commonly associated with chemicals that exterminate, kill or destroy a pest.  In fact the word ends with "cide", which means “kill”.  While many pesticides do in fact kill a pest not all are used for that purpose.   For example, certain pesticides, known as insect repellents, repel insects but do not actually kill them. Other types of pesticides, such as plant desiccants, are used to aid in the harvesting of the plants to which they are applied.  It is important to understand that the term pesticide applies to a broad group of chemicals and substances not just bug killers (insecticide) and weed killers (herbicides). 

It is easy to associate products sold to kill insects or weeds with the term pesticide but what about the following products:

  • Anti-fouling paints used on watercraft to prevent buildup of microorganisms, plants, algae and/or animals.
  • Aquarium products used to control algae, aiptasia, flatworms and other aquatic organisms
  • Rooting hormones applied to plant cuttings
  • Sterilants used in hospitals for infection control
  • Sanitizers used in restaurants on food prep surfaces, equipment and serving utensils (including glasses used to serve beverages) to prevent the spread of food borne illnesses such as salmonella or e. coli.
  • Biocides to control bacteria in fuel lines, oil rigs or gas wells.
  • The liquid that your beautician dips the comb into between clients.  Yes, it is a pesticide too (sanitizer/disinfectant).

As some of the above examples show, the term also applies to products used in the home to control microorganisms such as bacteria and viruses.  These products are known as antimicrobial pesticides and include disinfectants, sanitizers and sterilants.  Antimicrobial products are also used to control mold and mildew in the bathroom, algae in the pool, and slime build up in water lines.  In some cases, antimicrobial pesticides have been incorporated into other products such as plastics, adhesives or paints to protect the material from deterioration by microorganisms.   The term does not apply to substances, such as antiseptics or germicides, which control microorganisms that live on or in living man or other animals. 

In general, a pesticide could be defined in the following manner:

  1. Any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any insects, rodents, fungi, bacteria, weeds, or other forms of plant or animal life, bacterium, or viruses, except viruses living on or in living man or other animals or
  2. Any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant.

The ingredients in pesticides come from many sources, both natural and manmade.  Naturally derived pesticides, or biopesticides, are derived from plants, animals, minerals or microorganisms such as bacteria.  While pesticides are often associated with poisons, some actually come from plant oils or spices commonly consumed by people.  These pesticides could contain ingredients such as cinnamon, garlic, corn oil, mint oil or other similar substances.  Conventional and synthetic pesticides are chemicals that have been developed in a laboratory either by using manmade materials or by combining natural and manmade materials together.  In some cases, the manmade ingredients are formulated based on the chemistry of a natural substance.  Pyrethrins, for example, are chemicals that were created in a laboratory based on pyrethrum, a chemical found in chrysanthemums and other related plants. 

Pesticides can be used in numerous places for a variety of applications.  Insecticides play a significant role in agricultural by reducing the insect populations and increasing plant productivity.  Insect repellents serve as a first line of defense against ticks and mosquitoes which carry various diseases. Disinfectants and sanitizers prevent the spread of disease and infections by controlling bacteria and viruses on surfaces in hospitals, restaurants and homes.   Some pesticides prevent slime buildup in water or oil pipes which reduces maintenance and helps keep the fluid flowing efficiently.  Of course, as will be discussed in other areas of this website, there are times when pesticides are not the only tool for pest management. 

Most pesticides can be identified by the presence of an EPA Registration Number which appears on their label.  This indicates that the product has been registered by the Environmental Protection Agency (EPA) as a pesticide.  The EPA carries out the provisions of the Federal Insecticide, Fungicide and Rodenticide Act.  Companies that produce federally registered products have provided EPA research data that describes the products toxicity to humans, animals and the environment.  They have also submitted evidence that the product will be effective against the pests which appear on the specific product label when it is used according to the label directions. 

There are a smaller number of pesticides which are not required to have EPA registration numbers.  The ingredients in such products are believed to present minimal risk to the end-user.  These products are commonly referred to as 25(b) Exempt or Minimum Risk Products.  The EPA has published a list of ingredients, both active and inert, which can be used in these products.  This list is published on EPA’s Minimum Risk Pesticides page.  Since these products are not registered federally, the manufacturers are not required to submit evidence of their effectiveness to EPA. 

In summary, the term pesticide applies to a large number of substances even those which are “homemade”.  If any claim is made that a substance prevents, destroys, repels, or mitigates any type of pest then it is a pesticide.  Consumers need to be cautious of products that make claims that they control or repel a pest yet indicate they do not contain a pesticide.  They also need to be aware that many of the products that they use around their home are pesticides.  Users need to understand the potential risks and take all necessary precautions to minimize their exposure to pesticides.  It is essential to follow the label to reduce exposure to humans and the environment.

In addition to the resources found on the Virginia Pesticide Safety website, you will find the following resources beneficial in understanding pesticides and pest management:
EPA, Pesticide Programs
Virginia Tech Pesticide Programs (VTPP)
Pesticide Environmental Stewardship
Types of Pesticides (NPIC)