A. PESTICIDES: What are they?

The term pesticides represents a substance or mixture of substances intended to prevent, destroy, repel or mitigate any pest. A pesticide can also be a plant regulator, defoliant or desiccant.

B. Pesticide classifications

Pesticides can be classified four different ways: formulation, target, mode of action, and chemistry. Table I shows several common formulations. Table II shows pesticide targets or sites of use. Table III shows modes of action. Table IV shows some pesticide chemistries.

Each group of pesticides comes with its own set of hazards. The insecticides and fumigants present some of the greatest hazards in terms of acute toxicity. However, the bipyridyl herbicides also present extreme acute toxicity hazards.

Table II shows pesticide targets or sites of use.

Table III shows some pesticide modes of action. The nerve poisons include several modes of action. The largest number insecticides are cholinesterase inhibitors. Several herbicides, fungicides and plant growth regulators also are cholinesterase inhibitors. These include the organophosphates and carbamates.

Pesticides do not fit into a neat group of chemical families. Although the largest number of pesticides fit into the organophosphate group. Recent pesticide developments that look for specific biochemical targets have produced an enormous diversity in the chemistry involved in pest control. The second largest class of chemicals registered as insecticides includes a broadly diverse group of terpenoid compounds known collectively as pheromones. Ten years ago there were essentially four groups of insecticidal compounds. Now there are more than fifteen.

Herbicides present an even more bewildering diversity. Not only do they include all the chemistries involved in the insecticides, they also include more than forty additional chemical groups.

Fungicides, antimicrobials, vertebrate poisons, and other miscellaneous pest control compounds simply add to the array of commercial poisons now on the market.

Table IV shows the wide variety of pesticides available in the market. Specific treatment for many of them requires calling special pesticide "hot lines" maintained by chemical companies to deal with poisoning and exposure emergencies.

 Table of Contents | Preface | Section I | Section II | Section III | References