Biotic Stress and Yield Loss PDF

Preface

The idea for this book came to us after we organized a symposium at the 1996 meeting of the North Central Branch of the Entomological Society of America. The symposium was titled Understanding Yield Loss from Insects and its focus was on current knowledge of insect herbivores and their impact on plant fitness and yield loss. When we discussed the idea, we recognized it would be important to cover all biotic stressors (insects, plant pathogens, and weeds) because it is critical to compare and contrast plant responses to all biotic stressors if we are ever going to develop more encompassing understandings of plant stress. The participation of writers from many areas was essential for this project, and we are greatly appreciative of the contributions from our authors for this volume. We also appreciate and thank Marijean Peterson for her editorial reviews and assistance in manuscript preparation.

This book is a natural extension of a previous volume, Economic Thresholds for Integrated Pest Management, edited by Higley and Pedigo. Where that book focused on economic decision levels and pest management for insects, plant pathogens, and weeds, this book concentrates on plant physiological, developmental, growth, and yield responses to biotic stress. Most of the chapters discuss biotic stress primarily within an agricultural context. This largely reflects the current state of knowledge for plants and biotic stress. Much more is known about biotic injury and agricultural crops than biotic injury and wild plants within ecosystems. Many of the chapters also discuss plant response and yield loss to insect herbivores. This is partly a reflection of our backgrounds and disciplinary bias, but is also a reflection of the relative richness of entomological research efforts to characterize plant responses to insect injury.

This is not to imply that our understandings of biotic stress and plant response are adequate. To our knowledge, this is the first book to cover the topic of biotic stress and yield loss. Although one type of biotic stress—arthropod injury—may be better understood than the others, plant responses to biotic stresses continue to be largely ignored and poorly understood. Indeed, the term plant stress has been synonymous with the abiotic stresses—temperature, moisture, and mineral nutrition stress. We need to elevate our knowledge of biotic stress to the same level as abiotic stress if we are to meaningfully comprehend biotic stress and integrate both abiotic and biotic stress into a general understanding of plant stress.

One theme that emerges from many chapters in this volume is the need to regard stress as a general phenomenon affecting plants. Although there are profound differences between plants grown in agroecosystems and natural ecosystems, to us, one of the most appealing features of focusing on biotic stress is the potential for greater integration of plant ecophysiology. Many authors have recognized the schism between work on biotic stress in the basic and applied sciences (research on herbivory offers one striking example). As discussions in this book point out, it is time to look for commonalities and exploit the advantages offered by work in both sys-tems. Asimilar appeal can be made for research that spans disciplines. Happily, over the 15 years we have been working in this area, we have seen disciplinary boundaries weaken. Such a change is hardly surprising, given the intrinsically interdisciplinary nature of work in ecophysiology, and is welcome as the best hope for improving our understandings of plant stress.

Finally, our dedication of this volume to Larry Pedigo is fitting on many levels. Both of us studied under Larry: Bob as an undergraduate and Leon for both his graduate degrees. Larry established a research program that not only offered students the opportunity to work on state-of-the-art issues in pest management, but also encouraged students to look beyond where we were in entomology and pest management and seek a different future. Our later, postgraduate research on photosynthesis, yield loss, and stress would not have been possible without Larry's early encouragement. And, we have had the wonderful opportunity to make the transition from students to collaborators, so that our continued research and writing with Larry has been one of the most valued aspects of our careers.

Looking beyond this personal connection, it was Larry, along with his student Jay Stone, who recognized the importance of yield loss and stress in defining economic damage. Stern and co-workers rightly receive credit for inventing the economic injury level (EIL) and key concepts in 1959 that lead to the development of integrated pest management. But, there were no calculated EILs until Stone and Pedigo in 1972 showed how to do it. Their seminal contribution is that they linked data on economics with data on yield loss from pests. In doing so they helped define what a pest is and showed how understandings of stress are as important as understandings of pest population biology. Starting with that 1972 paper, Larry's work with his students on EILs, defoliation, yield loss, and stress interactions has helped move pest management beyond pests and pest populations to questions of economics and of plant stress.

It is our hope that this book will continue that journey.