My intent in writing this book has been to present an introduction to the many different types of natural enemies used for biological control, in the context of an overview of biological control methods and uses. This book grew from a course that I've taught for undergraduates at Cornell University. Many of my students have little background in entomology, plant pathology, or weed science but they are interested in biological control. My major goal with my course has been to make it possible for a greater breadth of people to learn about this subject. The first major book focusing specifically on biological control of insect pests and weeds was published in 1964 (DeBach, 1964a) and the first major book focusing on biological control of plant pathogens was published in 1974 (Baker & Cook). Since these first treatises, there have been numerous excellent books on biological control. The majority of these books are more detailed and are intended for professionals in this field. Some introductory books currently available are very basic or only cover a specific type of biological control. Therefore, I saw the need for a book such as this.

I find the interactions between natural enemies and their hosts fascinating and I feel that it makes sense to use these relationships to control pests whenever possible. Our challenge with biological control is to figure out how to manipulate these relationships to control pests.