ABSTRACT
I. INTRODUCTION Pesticides occupy a rather unique position among the many chemicals that humans encounter, in that they are deliberately added to the environment for the purpose of injuring or killing some form of life: ‘‘pests’’ in this connotation (Murphy, 1975). A pest is defined as a species that, owing to its numbers, behavior, or feeding habits, is able to inflict substantial harm on humans or their valued resources (van den Bosch, 1989). Today, pests annually destroy approximately 37% of all food and fiber crops in the world (Pimental and Levitan, 1986). The term pesticide is a general term and includes a variety of chemicals with different uses. As a group, for purposes here, they include insecticides, those chemicals having direct toxic effects on noxious insects; herbicides, agents having the capability to destroy unwanted plants; and fungicides, chemicals that eradicate undesirable fungi. These three categories constitute approximately 90% of all pesticide use in agriculture (Oller et al., 1980). The National Research Council in 1987 indicated that by expenditure, 66% of pesticides used were herbicides, 23% insecticides, and 7% fungicides. A miscellaneous group is also included in this work for those pesticides not characterized by these categories.
