S-64
Safety Makes Sense ... with pesticides on the farm
by Glen Lehker, Extension Entomologist, Department of Entomology
In his continual struggle against the many insects, weeds, and other organisms injurious to agricultural production, the farmer must use chemicals known as pesticides. In fact, 87 per cent of all pesticides are used for agricultural purposes.
WHAT IS A PESTICIDE?
Perhaps this question can best be answered backwards by saying that the following materials are most commonly referred to as pesticides:
•	Insecticides—used to kill insects.
•	Herbicides—used to kill weeds and unwanted plants.
•	Fungicides—used to prevent and kill organisms causing plant diseases.
•	Rodenticides—used to kill rodents such as rats and mice.
•	Acaracides—used to kill mites.
•	Nematicides—used to kill nematodes.
•	Avicides—used to kill pest birds.
HOW DO PESTICIDES DIFFER?
The USDA has registered more than 60,000 pesticide formulations involving about 900 active ingredients. These pesticides range in classification from high toxicity-high hazard to extremely low toxicity-no hazard. In this sense toxicity refers to the capacity of the undiluted chemical to cause injury to humans, and hazard refers to the possibility of its use causing injury. For example, a material with a high toxicity may not be highly hazardous if it is used in a very low concentration. On the other hand, a pesticide of moderate toxicity may be more hazardous if it is used in a high concentration.
Another means of classifying pesticides is by how long they last in the environment. There are those materials which have a long residual, those that break down almost immediately, and all degrees of variation between these two extremes.
Pesticides may also be classified according to the type of chemical compound. Among the more common groups are chlorinated hydrocarbons, organophosphates, carbamates, and heavy metal compounds.
As an example of how a particular pesticide fits into these categories, take the insecticide DDT. First, DDT is of only moderate toxicity and very little hazard is involved in its use. It is a very long-lasting material and it belongs to that class of compounds often referred to as the chlorinated hydrocarbons.
It is impossible in a brief publication such as this to discuss or even list all of the many pesticides that are on the market today. It should be remembered that they are all different and require individual precaution.
Cooperative Extension Service, PURDUE UNIVERSITY, Lafayette, Indiana