Posted 10/29/2015 |
Pest control, which had begun with simple tools and methods, was refined over centuries and completely reborn during World War II. The late 19th and early 20th century world of the first synthetic organic chemicals gave rise to the first modern synthetic pesticides in the form of organochloride compounds.
Many organochloride compounds, such as BHC and DDT, were first synthesized in the 1800’s, but their properties as insecticides were not fully discovered and exploited until the late 1930’s. BHC (Benzene hexachloride) was first produced by the English scientist, Michael Faraday, in 1825. Its properties as an insecticide were not identified until 1944. DDT (dichlorodiphenyltrichloroethane) was first prepared by Othmar Ziedler, an Austrian chemist, in 1825. The insecticidal properties of DDT were discovered by the Swiss chemist Paul Hermann Müller in 1939. This discovery led to Müller’s Nobel Prize in 1948.
This organochloride class of pesticides grew out of those initial discoveries and, through 1930-1970’s, developed into the range of organochloride pesticides known today. Primarily, there are two groups of organochloride pesticides: chlorinated alicyclic and cyclodiene compounds (Aldrin, Dieldrin, Endrin, Heptachlor, Chlordane and Endosulfans), and the DDT compounds (DDD, DDE, etc.) The chlorinated alicyclics and cyclodienes bind to active sites in nerve processes leading to depression of the central nervous system.
The DDT compounds work on the peripheral nervous system, interrupting the axon’s ability to complete repolarization after activation and membrane depolarization.
The discovery of DDT for pesticide use was a huge boon to the war efforts. Prior to the discovery of DDT, pyrethrins were one of the major insecticides in use. However, pyrethrins were extracted from natural sources, primarily from flowers of the genus Chrysanthemum (Pyrethrum), supplies of which were limited and could not meet the demands of wartime needs.
DDT became the insecticide of choice for Allied Forces to control insects that were vectors for typhus,
malaria and dengue fever.
At the time, DDT was seen as a broad spectrum insecticide with low toxicity to mammals. It was inexpensive to produce, easy to apply to large areas and was persistent, so that reapplication was generally not needed; DDT is insoluble in water and therefore was not washed away by weather. The compound appeared, at first, to be incredibly effective at eliminating the insect vectors of disease and was hailed as a wonder insecticide.
By 1945, DDT was made available for agricultural applications. By the 1950’s the first signs of insect resistance to DDT began to appear. In 1962, Rachel Carson, a marine biologist and conservationist, published Silent Spring. Her book highlighted the detrimental effects of pesticides on the environment. The widespread popularity of her book started many grassroots organizations which called for more environmental protections and strict controls on pesticide use.
Part of the call to change was the reduction or removal of DDT, and many other pesticides developed in the 1940’s-1960’s, from the pest fighting arsenal.
DDT was in widespread use around the world until the 1970’s and 1980’s. The EPA canceled most uses of DDT by 1972. Many other countries shortly followed suit, by removing DDT from most agricultural applications. In 2004, the Stockholm Convention outlawed many persistent organic pollutants (POPs) and restricted the use of DDT to vector control (primarily for malaria). Despite the worldwide restrictions and bans on DDT, as of 2008, India and North Korea were still using DDT in agricultural applications. India is the sole country in the world still producing DDT.
Since the start of the production boom in the 1940’s to present day, a huge catalog of thousands of insecticides, herbicides and general pesticides was developed, including organochlorides (DDT, BHC), organophosphates (Parathion, Malathion, Azinophos methyl), phenoxyacetic acids (2,4-D, MCPA, 2,4,5-T), Captan, Carbamates (Aldicarb, Carbofuran, Oxamyl, Methomyl) neonicotinoids (Imidacloprid, Acetamiprid, Clothianidin, Nitenpyram) and Glysophates.
The neonicotinoids are neuro-active insecticides, similar to nicotine compounds, that were developed in the 1980’s and 1990’s. Of all the neonicotinoids, Imidacloprid has become one of the most abundantly used insecticides in the world. Patented in 1988 and registered with the EPA in 1994 by Bayer Crop Science, Imidacloprid works by disrupting the transmission of nerve impulses in insects by binding to an insect’s nicotinic acetylcholine receptors, resulting in paralysis and death of the insect. Imidacloprid is highly toxic to insects and other arthropods, including marine invertebrates. It is considered to be moderately toxic to mammals, if ingested at high dosages.
The acute toxicity and environmental fate of Imidacloprid and other neonicotinoid pesticides have been greatly debated since their adaptation in the 1990’s. Many studies question the persistence of neonicotinoids in water supplies and the ecological impacts to other environmentally and economically important arthropods. Studies published within the last two decades have linked bee colony collapse disorders with Imidacloprid and other similar pesticides. The most toxic pesticide in the world today for honey bees (Genus Apis) is also the most commonly used insecticide in the world, Imidacloprid.
If Imidacloprid is the most widely used insecticide in the world, Glyphosate is the most widely used herbicide in the world. Glysophate was developed by a Monsanto chemist, John E. Franz, in 1970. Roundup (as it was trademarked) quickly became one of the most popular herbicides in the world, by both, agricultural enterprises and home users. The mode of action for Glyphosate is to inhibit a plant enzyme which is part of the synthesis of aromatic amino acids. The inhibition of the amino acid production affects primarily the growing regions of the plants, killing plants in their growth cycle but not in their seed stage.
In 1994, the Roundup Ready Soybean was commercially approved in the United States. This genetically engineered soybean was created to be resistant to glyphosate. These types of crops allowed for the use glyphosate to control other pest plants without endangering the crop. The list of glyphosate resistant crops has grown since the introduction of the Roundup Ready Soybean to include: corn, canola, alfalfa, cotton and wheat.
Early genetic manipulation of plants and animals can be seen throughout history, manifested as selective breeding and pollination techniques employed to produce hardier and more disease resistant plants and livestock. The discovery of specific DNA sequences, which could be transferred from one organism to another, has only occurred within the last few decades. In 1983, a tobacco plant resistant to antibiotics became the first transgenic plant. Cotton followed in the 1990’s, and then came the ‘Round-Up-Ready’ Soybean. Genetically modified organisms (GMOs) have become widely used in the United States since their initial introduction in the 1990’s. Genetically modified crops are grown by millions of farmers in dozens of countries. The predominant modified crops are soybeans, corn or maize, cotton and canola.
As of 2010, 93% of soybeans, 78% of cotton, and 70% of corn were herbicide-resistant GMOs.
The United States is one the leading proponents for research into GMOs and surpasses most other countries,
growing 59% of the world’s GMO crops. The success of GMOs around the world has been mixed. Many European nations have experienced protests over GMOs and their safety- most of the controversy surrounds the actual process of altering the genetic structure of plants and whether or not those plants should require labeling.
The overall, general scientific opinion weighs in favor of the safety of GMO crops.
GMO labeling is required in many
countries but not in the United States. Scientists and economists argue that the potential benefits of GMO crop include reduction of the use of pesticides and other hazardous pollutants and the increase in the nutritional value and production of agricultural products. Opponents of GMOs claim that all the latent risks have not been adequately identified, especially the potential long-term impact on human health and the environment.
The issue is not if genetically modified organisms should be used as a pest control strategy. The truth is that genetic modification has become the newest tool in the arsenal of pest management, and it will be up to the future to decide if the history of this pest management strategy goes the same way as heavy metal pesticides and DDT or if l it will become the ultimate response to pest control.
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