Insecticides

An insecticide is a pesticide whose purpose is to kill or to prevent the multiplication of insects.

Insecticides are very widely used in agriculture, as well as in people's dwellings and workplaces. The use of insecticides is one of the major causal factors behind the increase in agricultural productivity in the 20th century.

Various plants have been used as folk insectides for centuries, including tobacco and pyrethrum.

Environmental Effects

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Some insecticides have been banned due to their adverse effects on animals or humans. Misuse of insecticides is a major factor in pollinator decline.

DDT is an example of a heavily used pesticide. One of the better known impacts of DDT is to reduce the thickness of the egg shells on predatory birds. The shells sometimes become too thin to be viable, causing reductions in bird populations. This occurs with DDT and a number of related compounds due to the process of bioaccumulation, wherein the chemical, due to its stability and fat solubility, accumulates to progressively higher concentrations in the body fat of animals farther up the food chain. The near-worldwide ban on agricultural use of DDT and related chemicals has allowed some of these birds--such as the peregrine falcon--to recover in recent years.

Despite these positive results of the reduction of DDT utilization, opponents of environmentalism often erroneously cite it as an example of environmentalism going too far and interfering with malaria eradication, going so far as to estimate the cost of human lives resulting from the DDT ban; for instance the novelist Michael Crichton states in his bestselling book, State of Fear:

"Since the ban, two million people a year have died unnecessarily from malaria, mostly children. The ban has caused more than fifty million needless deaths. Banning DDT killed more people than Hitler."

This accusation, while sensational, is erroneous, as no ban exists on the use of DDT for eradication of malaria or any other insect borne disease.[1] Groups fighting malaria have praised the ban on agricultural use of DDT, since it reduces the rate with which mosquitoes become resistant to DDT, which is the main reason it is not used more often to fight malaria:

"The outcome of the treaty is arguably better than the statu­­s quo going into the negotiations over two years ago. For the firs­t time­, there is now an insecticide which is restricted to vector co­ntrol onl­y, meaning that the selection of resistant mosquitoes wi­ll be slower th­an before." [2].

In fact, according to Agricultural production and malaria resurgence in Central America and India, Chapin, Georgeanne & Robert Wasserstrom, Nature, Vol. 293, 1981, page 183), the lives actually saved due to banning agricultural use of DDT can be estimated:

"Correlating the use of DDT in El Salvador with renewed malaria transmission, it can be estimated that at current rates each kilo of insecticide added to the environment will generate 105 new cases of malaria."

Some of the newer insecticides are more specific in their actions and are designed to break down into non-toxic components within a few days of application.

Application methods

Personal insecticide, commonly referred to as "bug spray", typically comes in a plastic bottle or aerosol can. Applied to clothing, arms, legs, and other extremities, the use of this pesticide will either ward off or kill nearby insects.

Insecticide used for killing pests—most often insects, and arachnids—primarily comes in an aerosol can, and is sprayed into the air or nest as a means of killing the animal. Fly sprays will kill house flies, blowflies, ants, cockroaches and other insects and also spiders.

Active ingredients of most bug sprays include permethrin and tetramethrin, which act on the nervous system of insects and arachnids.

Bug spray should be used in well ventilated areas only, as the chemicals contained in the aerosol and pesticide can be harmful or deadly to humans.

Individual insecticides

Chlorinated

Several are now banned because of their ecological persistence:

• Aldrin
• Chlordane
• Dieldrin
• DDT
• Endrin
• Lindane

Organophosphorus

Chemically similar to Nerve agents

• Diazinon
• Malathion
• Parathion

Plant toxin derived

• Derris (rotenone)
• Pyrethrum
• Neem (Azadirachtin)
• Nicotine