Chapter 24

Greenhouse Pesticides

Chemical Pesticides

Conventional pesticides (i.e., synthesized by the agrochemical companies) are man-made and are the largest group of pesticides used by growers. There are many classes of synthetic pesticides. The main classes consist of organochlorines, organophosphates, carbamates, and pyrethroids. The synthetic compounds include most of the insecticides, herbicides, and fungicides. If all other integrated pest management tactics are unable to keep an insect pest population below an economic threshold, then use of a pesticide to control the pest and prevent economic loss is justified. In most cropping systems, pesticides are still the principal means of controlling pests once the economic threshold has been reached.

Types of Chemical Pesticides

There are many classes of synthetic pesticides. The main classes consist of organochlorines, organophosphates, carbamates, and pyrethroids. Pesticides with similar structures have similar characteristics and usually have a similar mode of action. The chemical structure of organochlorines is diverse, but they all contain chlorine, which places them in a larger class of compounds called chlorinated hydrocarbons. Organophosphates were developed to replace some of the chlorinated hydrocarbons. Organophosphates break down more rapidly in the environment and are less likely to pose an environmental risk. However, they are, in general, more acutely toxic than chlorinated hydrocarbons. Organophosphates contain the element phosphorus linked to oxygen to form the phosphate group.

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