Preface

Arable weeds have been the major biotic cause of crop yield losses since the origins of agri‐ culture. Weeds result in 34% loss of crop yield, on average, worldwide. Herbicides are by far the most effective weed control tools ever developed, controlling 90 to >99% of the weeds targeted. Consequently, the arable surface treated and range of weed species targeted by herbicides increased rapidly worldwide after their development. Weed communities have evolved over time in response to this control practice imposed on them. For the past half century, a principal method of weed management in commercial crops in the most devel‐ oped countries has been the use of herbicides. But, this golden age of herbicides was quickly cut short, however, by the detection of the first herbicide-resistant weeds in the early 1970s, although it was described as a potential problem as early as 1957. Resistant weeds have been evolving worldwide from selection pressure caused by the repeated use of herbicides with the same mechanism of action in conventional crop cultivars. Today, herbicide resistance has been reported in 251 weed species (146 dicots and 105 monocots) in more than 670,000 fields in 90 crops in 66 countries. Resistance has been reported to all major known herbicide modes of action, and no new mode of action has been marketed since 1991.

Herbicide resistance in weeds is a global problem. Resistance to herbicides in arable weeds is increasing rapidly worldwide and threatening global food security. Resistance has now been reported to all major herbicide modes of action despite the development of resistance management strategies in the 1990s.

From the other side, development of herbicide-resistant crops has resulted in significant changes to agronomic practices, one of which is the adoption of effective, simple, low-risk, crop production systems with less dependency on tillage and lower energy requirements. Overall, the changes have had a positive environmental effect by reducing soil erosion, the fuel use for tillage, and the number of herbicides with groundwater advisories as well as a slight reduction in the overall environmental impact quotient of herbicide use. However, herbicides exert a high selection pressure on weed populations and density and diversity of weed community's change over time in response to herbicides and other control practices imposed on them.

This book focuses on the recent progress made in understanding the genetic and evolution‐ ary mechanisms underlying herbicide resistance in weeds. Current controversies on key as‐ pects of resistance evolution are discussed. The authors of *Herbicide Resistance in Weeds and Crops* highlight crucial present and future research directions and challenges connected with understanding of weed resistance development and the importance and impact of herbi‐ cide-resistant crops.

The information provided in this book serves as a beneficial device to illustrate current her‐ bicide resistance research touching agriculture and environment, as well. *Herbicide Resistance in Weeds and Crops* should be principally valuable for scientists and researchers interested in advancing research strategies concentrated on accepting weed resistance as a global prob‐ lem and proactive, evolutionary-based weed management options for agriculture today. I hope that this book will provide the scientific community with a source of crucial research knowledge to assist format prospective research and understanding weed and crop herbi‐ cide resistance.

#### **Dr. Zvonko Pacanoski**

Associate Professor of Weed Science, Institute for Plant Protection, Faculty of Agricultural Sciences and Food, Skopje, Republic of Macedonia

**Provisional chapter**
