Pesticide

A pesticide is a substance released into a culture to fight against organisms harmful. It is a generic term which includes the insecticides, the fungicides, the herbicides, the parasiticides. They respectively deal with insect pests, the mushrooms, the "weeds" and to pests. They include so called "plant" or "plant". In a wider sense, such as European legislation it may be regulators of growth, or substances that respond to public health problems (such as cockroaches in dwellings), public health (insect pests [Lice, fleas] or vectors of diseases such as malaria and pathogenic bacteria destroyed by water chlorination), animal health, or on non-agricultural areas (roads, airports, railways, electrical networks ...).

Aerial application of pesticides. This mode of application is the one most likely to pollute the air. It is little used in Europe but common in the United States.

Etymology

The etymology of the word pesticide is built on the model of many words ending with the suffix "-cide" which originates from the Latin verb "caedo, cadere," which means "kill." He was the assistant french root pest (animal, insect or weed) or the french word plague (evil, evil thing that corrupts disease), both derived from the Latin for "Pestis the scourge in general, and a dangerous disease in particular (but Emile Littré's dictionary 1872-1877 also cited Corssen who felt that had perdtis pestis (perdere, to lose, ruin).

History

Chemical control has been around for millennia: the use of sulfur goes back to Ancient Greece (1000 BC) and the arsenic is recommended by Pliny, Roman naturalist, as insecticide. Plants known for their toxic properties have been used as pesticides (eg aconite in the Middle Ages against rodents). Of treated plants were produced (eg poisons to treaty Maimonides in 1135). Products arsenical-based or lead (lead arsenate) were used in the sixteenth century in China and Europe.

The insecticidal properties of tobacco were known since 1690. In India, the gardeners used the roots of Derris and Lonchocarpus (rotenone) as an insecticide. Their use has spread to Europe around 1900.

The chemistry developed in the nineteenth century, providing many pesticides based mineral salts copper. The fungicides based on copper sulphate are spreading, especially the famous Bordeaux porridge (a mixture of copper sulphate and lime) for the fight against invasive fungal vine and potato, with effects of pollution on soil (copper degradable). Salts of mercury are used in the early twentieth century for the treatment of seeds.

Structure of a chemical insecticide, the DDT

 
Structural formula of the atrazine, herbicide of the triazine family

Pesticides (here the atrazine in the United States) are subject to use targeted geographically and temporally, which explains the strong regional and seasonal variations in water pollution and air from these products

The preparation and use of pesticides is governed by rules and precautions, because of their toxicity and sometimes the flammability of solvents

The era of synthetic pesticides really began in the 1930s, taking advantage of the development of organic chemistry and synthesis of research on chemical weapons during the First World War.
In 1874, Zeidler summarizes the DDT, Muller in 1939 which establishes the insecticidal properties. The DDT is marketed from 1943 and opens the way for the family of organochlorines. The DDT has dominated the market of insecticides to the early 1970s.

In 1944, the herbicide 2,4-D, a hormone copied on plant growth and still heavily used today, is synthesized.

The Second World War generated through the research undertaken for the development of warfare, the family of organophosphates, which since 1945 has seen considerable development still needed today to some of these products, such as malathion.

In 1950-55 developing in the United States herbicides from the family of substituted ureas (linuron, diuron), followed shortly by the herbicide group quaternary ammonium and triazines.

The benzimidazole-type fungicides and pyrimidine date of 1966, followed by fungicides and imidazoles TRIAZOLE said fungicide IBS (inhibitor of the synthesis of sterols), which currently represent the largest market for fungicides.

In 1970-80 the emergence of a new class of insecticides, the pyrethroids, which in turn dominate the market for insecticides.

Previously, the search for active ingredients was randomly subjecting many products for biological testing. When a product was chosen for these qualities biocides, we sought to improve efficiency through the synthesis of analogues. This procedure has allowed the development of synthesis techniques that are valid today.

Now the emphasis is on understanding the modes of action and the search for new targets. Knowing the target, then we can establish structure-activity relationships leading to the procurement of active ingredients. This is possible through the development of basic research in the fields of biology and chemistry and new tools provided by quantum chemistry, mathematics and computers which allow the modeling of these molecules future.

Currently, there is a market consolidation at the level of families most recently discovered with the search for new properties. At the same time, new physiological targets of the animal or plant are explored in order to develop products to original modes of action of products derived from biotechnology or chemical mediators.


Consumption

Tonnages used around the world have been rising steadily for 60 years. They appear to be declining in some countries in Europe, but we must also take into account the fact that dose or equal weight, the active ingredients of today are much more effective than those of previous decades, with France remaining in 2006 The second consumer of pesticides and third in 2007. Almost as much as the United States but with a land area 10 times smaller. France and Holland are the countries that consume the largest quantity of pesticides per hectare. France ailleus has been threatened by the European Commission to be condemned, failing to take necessary measures, to a fine of 28 million € uros for non-compliance with EU rules on pesticides.

The molecular change, is the need to circumvent the resistance of insects, fungi or plants, or to replace banned because of their toxicity, either because the molecules are considered more interesting replace others.

The pesticides most commonly used (in terms of quantity) are herbicides. The most active molecule sold as weed killer and the most used in the world is glyphosate.