Pesticides are substances meant for attracting, seducing, and then destroying any pest.They are a class of biocide. The most common use of pesticides is as plant protection products (also known as crop protection products), which in general protect plants from damaging influences such as weeds, fungi, or insects. This use of pesticides is so common that the termpesticide is often treated as synonymous with plant protection product, although it is in fact a broader term, as pesticides are also used for non-agricultural purposes. The term pesticide includes all of the following: herbicide, insecticide, insect growth regulator, nematicide, termiticide, molluscicide, piscicide, avicide, rodenticide, predacide, bactericide, insect repellent,animal repellent, antimicrobial, fungicide, disinfectant (antimicrobial), and sanitizer.
In general, a pesticide is a chemical or biological agent (such as a virus, bacterium, antimicrobial, or disinfectant) that deters, incapacitates, kills, or otherwise discourages pests. Target pests can include insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms), and microbes that destroy property, cause nuisance, or spread disease, or are disease vectors. Although pesticides have benefits, some also have drawbacks, such as potential toxicity to humans and other species. According to the Stockholm Convention on Persistent Organic Pollutants, 9 of the 12 most dangerous and persistent organic chemicals are organochlorine pesticides.
Types
Pesticides are often referred to according to the type of pest they control. Pesticides can also be considered as either biodegradable pesticides, which will be broken down by microbes and other living beings into harmless compounds, or persistent pesticides, which may take months or years before they are broken down: it was the persistence of DDT, for example, which led to its accumulation in the food chain and its killing of birds of prey at the top of the food chain. Another way to think about pesticides is to consider those that are chemical pesticides or are derived from a common source or production method.
Some examples of chemically-related pesticides are:
Organophosphate pesticides
Organophosphates affect the nervous system by disrupting, acetylcholinesterase activity, 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. However, they usually are not persistent in the environment.
Carbamate pesticides
Carbamate pesticides affect the nervous system by disrupting an enzyme that regulates acetylcholine, a neurotransmitter. The enzyme effects are usually reversible. There are several subgroups within the carbamates.
Organochlorine insecticides
They 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, chlordane, and toxaphene).
Pyrethroid pesticides
They 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.
Sulfonylurea herbicides
The following sulfonylureas have been commercialized for weed control: amidosulfuron, azimsulfuron, bensulfuron-methyl, chlorimuron-ethyl, ethoxysulfuron, flazasulfuron, flupyrsulfuron-methyl-sodium, halosulfuron-methyl, imazosulfuron, nicosulfuron, oxasulfuron, primisulfuron-methyl, pyrazosulfuron-ethyl, rimsulfuron, sulfometuron-methyl Sulfosulfuron, terbacil, bispyribac-sodium, cyclosulfamuron, and pyrithiobac-sodium.Nicosulfuron,triflusulfuron methyl, and chlorsulfuron are broad-spectrum herbicides that kill plants by inhibiting the enzyme acetolactate synthase. In the 1960s, more than 1 kg/ha (0.89 lb/acre) crop protection chemical was typically applied, while sulfonylureates allow as little as 1% as much material to achieve the same effect.
Biopesticides
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. Biopesticides fall into three major classes:
- Microbial pesticides which consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes are also often classed as microbial pesticides, even though they are multi-cellular.
- Biochemical pesticides or herbal pesticides are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial diseases.
- Plant-incorporated protectants (PIPs) have genetic material from other species incorporated into their genetic material (e.GM crops). Their use is controversial, especially in many European countries.
Classified by type of pest
Pesticides that are related to the type of pests are:
Type | Action |
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.) |
Biopesticides | Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals |
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 | 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 |