Insecticide and Related Topics

Pyrethroid

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Organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums .

Chemical structure of Permethrin isomers

(1R,3R)- or (+)-trans-chrysanthemic acid.

Pyrethroids are used as commercial and household insecticides.

General chemical structure of the organophosphate functional group

Organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure O=P(OR)3, a central phosphate molecule with alkyl or aromatic substituents.

Like most functional groups organophosphates occur in a diverse range of forms, with important examples including key biomolecules such as DNA, RNA and ATP, as well as many insecticides, herbicides, nerve agents and flame retardants.

Commercial product concentrate containing 50% DDT, circa 1960s

DDT

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Colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride.

Commercial product of Ciba-Geigy Néocide (powder box, 50 g) containing 10% DDT, made in France.

An airplane spraying DDT over Baker County, Oregon as part of a spruce budworm control project, 1955

Degradation of DDT to form DDE (by elimination of HCl, left) and DDD (by reductive dechlorination, right)

A U.S. soldier is demonstrating DDT hand-spraying equipment. DDT was used to control the spread of typhus-carrying lice.

Spraying hospital beds with DDT, PAIGC hospital of Ziguinchor, 1973

Biomagnification is the build up of toxins in a food chain. The DDT concentration is in parts per million. As the trophic level increases in a food chain, the amount of toxic build up also increases. The X's represent the amount of toxic build up accumulating as the trophic level increases. Toxins build up in organism's tissues and fat. Predators accumulate higher toxins than the prey.

Originally developed as an insecticide, it became infamous for its environmental impacts.

Pesticide

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Pesticides are substances that are meant to control pests.

A Lite-Trac four-wheeled self-propelled crop sprayer spraying pesticide on a field

A sign warning about potential pesticide exposure

The cholinergic synapse and the breakdown of acetylcholine into choline and acetate by acetylcholinesterase.

Preparation for an application of hazardous herbicide in the US

This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampricide.

Neonicotinoid

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Neonicotinoids (sometimes shortened to neonics ) are a class of neuro-active insecticides chemically similar to nicotine.

Malaria

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Mosquito-borne infectious disease that affects humans and other animals.

The life cycle of malaria parasites. Sporozoites are introduced by a mosquito bite. They migrate to the liver, where they multiply into thousands of merozoites. The merozoites infect red blood cells and replicate, infecting more and more red blood cells. Some parasites form gametocytes, which are taken up by a mosquito, continuing the life cycle.

Micrograph of a placenta from a stillbirth due to maternal malaria. H&E stain. Red blood cells are anuclear; blue/black staining in bright red structures (red blood cells) indicate foreign nuclei from the parasites.

Electron micrograph of a Plasmodium falciparum-infected red blood cell (center), illustrating adhesion protein "knobs"

The blood film is the gold standard for malaria diagnosis.

Ring-forms and gametocytes of Plasmodium falciparum in human blood

An Anopheles stephensi mosquito shortly after obtaining blood from a human (the droplet of blood is expelled as a surplus). This mosquito is a vector of malaria, and mosquito control is an effective way of reducing its incidence.

Man spraying kerosene oil in standing water, Panama Canal Zone, 1912

Walls where indoor residual spraying of DDT has been applied. The mosquitoes remain on the wall until they fall down dead on the floor.

An advertisement for quinine as a malaria treatment from 1927.

Deaths due to malaria per million persons in 2012

Past and current malaria prevalence in 2009

Ancient malaria oocysts preserved in Dominican amber

British doctor Ronald Ross received the Nobel Prize for Physiology or Medicine in 1902 for his work on malaria.

Chinese medical researcher Tu Youyou received the Nobel Prize for Physiology or Medicine in 2015 for her work on the antimalarial drug artemisinin.

Artemisia annua, source of the antimalarial drug artemisinin

U.S. Marines with malaria in a field hospital on Guadalcanal, October 1942

Members of the Malaria Commission of the League of Nations collecting larvae on the Danube delta, 1929

1962 Pakistani postage stamp promoting malaria eradication program

Disability-adjusted life year for malaria per 100,000 inhabitants in 2004
no data
<10
0–100
100–500
500–1000
1000–1500
1500–2000
2000–2500
2500–2750
2750–3000
3000–3250
3250–3500
≥3500

The risk of disease can be reduced by preventing mosquito bites through the use of mosquito nets and insect repellents or with mosquito-control measures such as spraying insecticides and draining standing water.

Insect repellent

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Substance applied to skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface.

Oil Jar in cow horn for mosquito-repelling pitch oil, a by-product of the distillation of wood tar. Carried in a leather strap on a belt. Råneå, Norrbotten, since 1921 in Nordiska museet, Stockholm.

Some insect repellents are insecticides (bug killers), but most simply discourage insects and send them flying or crawling away.

Imidacloprid

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Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects.

Bacillus thuringiensis

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Gram-positive, soil-dwelling bacterium, the most commonly used biological pesticide worldwide.

Gram stain of Bacillus thuringiensis under 1000 × magnification

Bt toxins present in peanut leaves (bottom dish) protect it from extensive damage caused to unprotected peanut leaves by lesser cornstalk borer larvae (top dish).

Agriculture enthusiasts examining insect-resistant transgenic Bt corn

An ovitrap collects eggs from mosquitoes. The brown granules in the water are a B. t. israelensis preparation that kills hatched larvae.

During sporulation, many Bt strains produce crystal proteins (proteinaceous inclusions), called delta endotoxins, that have insecticidal action.

Pesticide application can artificially select for resistant pests. In this diagram, the first generation happens to have an insect with a heightened resistance to a pesticide (red). After pesticide application, its descendants represent a larger proportion of the population, because sensitive pests (white) have been selectively killed. After repeated applications, resistant pests may comprise the majority of the population.

Pesticide resistance

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Previously effective at controlling the pest.

The Insecticide Resistance Action Committee (IRAC) definition of insecticide resistance is a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species.

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