Some science behind the scenes


In general, a pesticide is a chemical or biological agent (such as a virus, bacterium, parasite or fungus) that deters, incapacitates, kills, or otherwise discourages 'pests'.  A pest is defined as anything that the particular human being using this substance finds objectionable, unwanted, a nuisance, or a threat - bodily threat or financial threat.

Thus target 'pests' can include insects, commercial plant pathogens, 'weeds' [unwanted plants], molluscs, birds, mammals, fish, reptiles, bacteria, fungi, parasites, viruses and other microbes.  As can be seen the definition thus includes practically every living thing on the earth.  If that human being has decided he doesn't want it - it is a 'pest' and pesticides are the chemical and biological agent used to kill the unwanted creature. It is not until one sees the list of different killing agents used by man one realises that human beings are intent on killing  - theoretically I could have added guns and other weapons to the list, or gas chambers....................

As Wikipedia so aptly put it " some pesticides have drawbacks, such as potential toxicity to humans and other species."

Examples include:

Acaricides - pesticides that kill members of the arachnid subclass Acari, which includes ticks and mites.

  • "Ixodicides" are substances that kill ticks
  • "Miticides" are substances that kill mites.
  • “Scabicide”  target Sarcoptes.  Scabies  is a contagious skin infestation by the mite Sarcoptes scabiei

An algaecide or algicide - is a substance used for killing and preventing the growth of algae.

Animal pesticides - include

  • Animal repellents -  designed to keep certain animals away from objects, areas, people, plants, or other animals.  They include Mammal repellants
  • Rodenticides - a category of pest control chemicals intended to kill rodents. 

Avicide  - is any substance (normally, a chemical) which can be used to kill birds

Bactericide or bacteriocide - a substance that kills bacteria. Bactericides are generally for use externally and include disinfectants and antiseptics, antibiotics are not normally included as they are internally administered

Defoliant - any chemical sprayed or dusted on plants to cause its leaves to fall off. A classic example of a highly toxic defoliant is Agent Orange.  Defoliants differ from herbicides in that the former seeks mainly to strip leaves from plants, and the latter is used to destroy or inhibit the growth of plants.  They are used in commercial potato harvesting.  Diquat , for example, is a non-selective herbicide that damages only those parts of the plant to which it is applied. It has been used in pre-harvest crop desiccation. 

Fungicides  - are biocidal chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungicides are used both in agriculture and to fight fungal infections in animals. Chemicals used to control oomycetes, which are not fungi, are also referred to as fungicides as oomycetes use the same mechanisms as fungi to infect plants.

Herbicides - also commonly known as weedkillers, are pesticides used to kill 'unwanted plants' [ie unwanted by the person who is killing them]. Herbicides are widely used in commercial agriculture and landscape turf management. In the US, they account for about 70% of all agricultural pesticide use

Insecticide - a chemical used against insects. They include ovicides and larvicides used against the eggs and larvae of insects, as well as those used directly against the insects themselves. "Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans; and others may be found in the food chain".  These include:

  • Antifeedants – insecticides which discourage feeding
  • Chemosterilants - A chemo-sterilant is a chemical compound that causes reproductive sterility in an organism. 
  • Insect attractants - chemicals that attract insects and thus can be used to  trap them
  • Insect repellants - chemicals that can be used to repel insects
  • Mating disrupters (MD) - involves the use of synthesized sex pheromones to disrupt the reproductive cycle of insects

Molluscicides - also known as snail baits and snail pellets, are pesticides against molluscs, which are usually used in agriculture or gardening, in order to control gastropod pests specifically slugs and snails

Nematicide -  is a type of chemical pesticide used to kill plant-parasitic nematodes

Virucide - alternatively spelled 'viricide' and 'viruscide', is an agent (physical or chemical) that deactivates or destroys viruses. This differs from an antiviral drug which inhibits the development of the virus

Organophosphate-containing pesticides -  refers to a group of insecticides, organophosphates make up about 50% of the killing agents in chemical pesticides.  The human and animal toxicity of OPPs make them a societal health and environmental concern; the EPA banned most residential uses of organophosphates in 2001, but their agricultural use, as pesticides on fruits and vegetables, is still permitted,  as is their use in mosquito abatement in public spaces such as parks.  As of 2010, forty OPPs were registered for use in the U.S, for example

methyl parathion





see also

RECOGNITION AND MANAGEMENT OF PESTICIDE POISONINGS - James R. Roberts, M.D., M.P.H.Professor of Pediatrics, Medical University of South Carolina; J. Routt Reigart, M.D. Professor Emeritus, Medical University of South Carolina
US Environmental Protection Agency - there is a chapter on long term to pesticides over time and its links with chronic disease


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