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Ecologically Based Weed Management Protect crop yields and strengthen ecosystems with this essential guide Research into weed management is an increasingly critical component of both environmental stewardship and food production. The potential cost of weed propagation can be measured in crop yield reductions, under-nourished populations, stymied economies, and more. The propagation of herbicide-resistant weed populations means that purely chemical weed management is no longer viable; food production can now be secured only with an ecological approach to weed control. Ecologically Based Weed Management details such approaches and their potential to manage weeds across a range of agricultural and environmental contexts. It emphasizes the deployment of ecological principles to prevent weed infestations, reduce crop losses, and strengthen ecosystems. In a time when growing population and changing climates are placing enormous pressure on global food production, this approach to weed management has never been more vital. Ecologically Based Weed Management readers will also find: * A global team of expert contributors to a multidisciplinary approach * Detailed discussion of topics like herbicide limitation, integrated weed management, and more * Insights pertinent to agriculture, academia, government, industry, and more Ecologically Based Weed Management is ideal for researchers in agriculture chemistry, weed science, agronomy, ecology, and related fields, as well as for regulators and advanced students.
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Ecologically Based Weed Management
Concepts, Challenges, and Limitations
Edited by
Nicholas E. Korres
University of IoanninaKostakii, Greece
Ilias S. Travlos
Agricultural University of AthensAthens, Greece
Thomas K. Gitsopoulos
Hellenic Agricultural OrganizationDemeter, Greece
This edition first published 2024
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Library of Congress Cataloging-in-Publication Data
Names: Korres, Nicholas E., editor. | Travlos, Ilias S., editor. | Gitsopoulos, Thomas K., editor.
Title: Ecologically based weed management : concepts, challenges, and limitations / edited by Nicholas E. Korres, Ilias S. Travlos, Thomas K. Gitsopoulos
Description: First edition | Hoboken, NJ : John Wiley & Sons, 2024 | Includes bibliographical references and index.
Identifiers: LCCN 2023045924 (print) | LCCN 2023045925 (ebook) | ISBN 9781119709664 (hardback) | ISBN 9781119709725 (pdf) | ISBN 9781119709756 (epub) | ISBN 9781119709763 (ebook)
Subjects: LCSH: Weeds--Biological control. | Weeds--Control. | Weeds--Integrated control.
Classification: LCC SB611.5 .E36 2024 (print) | LCC SB611.5 (ebook) | DDC 632/.5--dc23/eng/20231031
LC record available at https://lccn.loc.gov/2023045924
LC ebook record available at https://lccn.loc.gov/2023045925
Cover Images: Courtesy of Nicholas E. Korres
Cover Design: Wiley
Set in 9.5/12.5pt STIXTwoText by Integra Software Services Pvt. Ltd, Pondicherry, India
Contents
Cover
Title Page
Copyright Page
Preface
List of Contributors
List of Reviewers
1 Ecologically Based Weed Management (EbWM): Enabling and Reinforcing the Approach
1.0 Introduction
1.1 Basis for a Sucessful Ecologically Based Weed Management Approach
1.2 Enabling and Reinforcing EbWM Principles in All Crop Production Systems
1.2.1 Systems Approach
1.2.2 Increased Biodiversity in the System
1.2.3 Inclusion of the Spatial Scale in the System: From the Field to the Landscape
1.2.4 Significant Improvement in the Objectives of the Crop Breeding Programs
1.2.5 Use of Herbicides Only Based on Dose-Response Technology
1.2.6 Calculation of Pesticide Load in Each Field
1.3 Projects / Experiments Where EwBM Principles Are Being Tested
1.3.1 Example 1
1.3.2 Example 2
1.3.3 Example 3
1.3.4 Example 4
1.3.5 Example 5
1.4 Concluding Remarks
2 Ecologically Based Weed Management: Implications and Agroecosystem Services
2.0 Introduction
2.1 Agro- and Natural Ecosystem Services
2.2 Do Weed Management Practices Negatively Affect Ecosystem Services?
2.3 Weed Management Practices that Enhance Ecological Services
2.4 Conclusions
3 Climate Change and Ecologically Based Weed Management
3.0 Introduction
3.1 Climate Change and Weeds
3.1.1 CO
2
Enrichment
3.1.2 Increased Temperature
3.1.3 Elevated CO
2
and Temperature
3.1.4 Precipitation Extremes and Water (Drought and Flood)
3.2 Climate Change and Weed Management
3.3 Ecologically Based Weed Management
3.3.1 Need for Ecologically Based Weed Management
3.3.2 Progress
3.4 Managing Weed Soil Seedbank Using Preventive Measures
3.4.1 Weed Seed Elimination/Destruction at Crop Harvest
3.4.2 Weed Seed Burial by Tillage
3.4.3 Utilizing Stale Seedbed Technique
3.5 Application of Principles of Conservation Agriculture for EWM
3.5.1 Minimal Soil Disturbance
3.5.2 Soil Cover by Retaining Crop Residues in the Crop Field
3.5.3 Crop Rotations
3.5.4 Weed and Crop Diversity
3.5.5 Weed Suppressive Cover Crops Inclusion in the Cropping Systems
3.5.6 Intercropping
3.5.7 Enhancing Crop Competitiveness against Weeds
3.5.8 Method of Crop Establishment
3.6 Crop Competitiveness
3.6.1 Competitive Crop Cultivars
3.6.2 Quicker Canopy Closure
3.7 Soil Solarization
3.8 Mechanical Weed Management
3.9 Biocontrol
3.10 Herbicide Use and EWM
3.11 Conclusions
4 The Ecological Base of Nonchemical Weed Control
4.0 Introduction
4.1 Physical Weed Control
4.1.1 Mechanical Weed Control
4.1.2 Harrows and Rotary Hoes
4.1.3 Inter-row Cultivation
4.1.4 Intra-row Cultivation
4.1.5 Innovative Implements for In-row Crops
4.1.6 Cutting and Mowing
4.2 Soil Tillage
4.2.1 Effect of Tillage on Weed Seeds
4.2.2 Vertical Weed Seed Distribution
4.2.3 Modifying Seed Germination Environment
4.2.4 Weed Seed Viability
4.2.5 Effect of Tillage Practice on the Growth and Establishment of Seedlings
4.2.6 Effect of Tillage on Asexual Reproduction Organs of Perennial Weeds
4.3 Thermal Weed Control
4.4 Mulching
4.5 Biological Weed Control
4.5.1 Classical Weed Biocontrol
4.5.2 Bioherbicides
4.5.3 Conservative Measures
4.6 Allelopathy
4.7 Cultural Weed Control
4.7.1 Enhancing the Competitive Ability of Crops
4.7.2 Water and Fertilizer Management
4.7.3 Crop Density and Arrangement
4.7.4 Date of Crop Establishment
4.8 Crop Diversification for Weed Management
4.8.1 Intercropping
4.8.2 Crop Cultivar (Genotype)
4.8.3 Crop Rotation
4.8.4 Cover Crops
4.9 Conclusions
5 The Underestimated Role of Cultural Practices in Ecologically Based Weed Management Approaches
5.0 Introduction
5.1 Role of Crop Diversification in Ecologically Based Weed Management
5.1.1 Role of Crop Rotation in Ecologically Based Weed Management
5.1.2 Role of Intercropping in Ecologically Based Weed Management
5.2 Role of Crop Competition in Ecologically Based Weed Management
5.2.1 Role of Competitive Cultivars and Competitive Hybrids in Ecologically Based Weed Management
5.2.2 Role of Increased Seeding Rates in Ecologically Based Weed Management
5.2.3 Role of Narrow Row Spacing in Ecologically Based Weed Management
5.3 Role of Sowing Timing in Ecologically Based Weed Management
5.4 Role of Irrigation and Fertilization Management in Weed Management
5.5 Conclusions
6 The Role of Agri-Chemical Industry on Ecologically Based Weed Management
6.0 Introduction
6.1 Herbicide Resistance
6.2 Climate Change
6.3 Environmentally Sound Weed Control Approaches
6.4 Environmentally Friendly Industry Initiatives
6.4.1 Syngenta Crop Protection AG
6.4.2 Bayer CropScience
6.4.3 FMC Corporation
7 Ecologically Based Weed Management to Support Pollination and Biological Pest Control
7.0 Introduction
7.1 Weed-Insect Interactions
7.1.1 Weeds and Pollinating Insects
7.1.2 Weeds and Natural Enemies
7.2 Weed Management to Support Pollination and Biological Control
7.2.1 Field Margins
7.2.2 Weed Management
7.2.3 Pollinators and Field Margins
7.2.4 Natural Enemies and Field Margins
7.2.5 Cover Crops
7.2.5.1 Current Status
7.2.5.2 Sowing and Termination
7.2.5.3 Impact on Weeds, Pollinators, and Natural Enemies
7.2.5.4 Cover Cropping Effect on Insect Pests
7.3 Challenges for Implementation of Ecological Weed Management in Practice
7.4 Conclusions
8 Use of Arthropods for Ecologically Based Weed Management in Agriculture
8.0 Introduction
8.1 Weed Biological Control in Agriculture
8.2 Biological Control in Cropping Systems
8.2.1 Case Study: Biological Control of
Solanum elaeagnifolium
Cav. (Solanaceae)
8.3 Biological Control in Grazing Lands
8.3.1 Case Study:
Hypericum perforatum
L. (Hypericaceae)
8.4 Biological Control in Plantations and Agroforestry Systems
8.4.1 Case Study: Biological Control of
Chromolaena odorata
R.M. King & H. Robinson (Asteraceae)
8.5 Biological Control in Aquatic Systems
8.5.1 Case Study:
Salvinia molesta
D.S. Mitchell (Salviniaceae)
8.6 Benefits of Biological Control
8.7 Conclusions
9 Ecologically Based Weed Management: Bioherbicides, Nanotechnology, Heat, and Microbially Mediated Soil Disinfestation
9.0 Biological Control of Weeds by Using Plant Pathogens
9.1 A Critical Assessment of the Role of Plant Pathogens in Weed Management
9.2 Expectations for the Future of Bioherbicides
9.2.1 Deleterious Rhizobacteria to Suppress Weed Growth and Competition
9.2.2 Weed Seedbank Management
9.2.3 Future Developments
9.3 Nonchemical Soil Disinfestation
9.3.1 Anaerobic Soil Disinfestation (ASD)
9.3.2 Steam
9.3.3 Soil Solarization
9.3.4 Biosolarization
9.3.5 Potential Mechanisms of Soil Disinfestation
9.3.6 Future Research Addressing Sustainability
9.4 Use of Nanocarriers to Deliver Active Ingredients (a.i)
9.4.1 Zein
9.4.2 Chitosan
9.4.3 Lignin
9.4.4 Viral Nanoparticles
9.4.5 Other Nanoformulations
9.5 Summary
10 Mechanisms of Weed Suppression by Cover Crops, Intercrops, and Mulches
10.0 Introduction
10.1 Traditional View of the Weed Seedbank
10.2 Alternative View of the Weed Seedbank and the Fate of Weeds
10.3 Mechanisms of Weed Suppression by Cover Crops, Intercrops, and Mulches
10.3.1 Seed Predation
10.3.2 Microbial Seed Decay
10.3.3 Residence Time
10.3.4 Allelopathy and Biochemical Inhibition
10.3.5 Germination Cues
10.3.6 Safe Sites
10.3.7 Resource Competition
10.4 Conclusions and Future Research Directions
11 Soil Seedbank from an Ecological Perspective
11.0 Introduction
11.1 The Soil Seedbank
11.1.1 Seedbank Types
11.1.2 Longevity
11.1.3 Spatial Distribution in the Seedbank
11.1.4 Seed Morphology
11.2 Contributions to the Soil Seedbank
11.2.1 Seed Dispersal
11.2.2 Seed Shatter and Retention
11.3 Reducing the Soil Seedbank
11.3.1 Dormancy
11.3.2 Germination
11.3.3 Death
11.4 Managing the Soil Seedbank
11.4.1 Cultural Management
11.4.1.1 Crop Rotations
11.4.1.2 Competitive Crops
11.4.1.3 Cover Crops
11.4.1.4 Intercropping
11.4.2 Mechanical Management
11.4.3 Biological Management
11.4.4 Chemical Management
11.5 Seedbank Response to Best Management Practices
11.6 Conclusions
12 The Role and Relationship of Tillage Systems with Ecologically Based Weed Management Approaches
12.0 Introduction
12.1 Tillage Systems
12.2 Ecologically Based Weed Management Approaches and Tillage Systems
12.2.1 Reduced Weed Seedling Recruitment from Weed Seedbank
12.2.2 Improved Crop Competitiveness
12.2.3 Reduced Weed Seedbank Size
12.3 Herbicide Efficacy, Herbicide Resistance, and Organic Farming
12.4 Conclusions
13 Ecologically Based Weed Management in Vegetable Crops
13.0 Introduction
13.1 Cultural Methods
13.1.1 Crop Rotation
13.1.2 Intercropping
13.1.3 Transplanting
13.1.4 False Seedbed
13.1.5 Inorganic and Organic Soil Cover
13.2 Preventive Methods
13.2.1 Field Choice
13.2.2 Cover Crops
13.3 Direct Methods
13.3.1 Biological Weed Control
13.3.2 Mechanical Weed Control
13.3.2.1 Current Stage
13.3.2.2 Inter and Intra Row Diversification
13.3.3 Robotic Weeding
13.3.4 Thermal Weed Control
13.4 Conclusion and Outlook
14 Ecological Weed Management in Row Crops
14.0 Introduction
14.1 Integrated Weed Management (IWM) in Row Crops
14.1.1 Preventing Weed Problems before They Start
14.1.2 Improve Crop Competition against Weeds
14.1.3 Keep Weeds “Off-Balance” – Do Not Let Them Adapt
14.1.4 Flame Weeding
14.2 Making a Weed Control Decision
14.2.1 Critical Period of Weed Control (CPWC)
14.2.2 Weed Threshold
14.3 Computer-Based Models and Decision Support Systems
14.4 Documentation and Record Keeping
14.5 Ecologically Based Weed Management in Row Crops – Final Thoughts
15 Practical Vegetable and Specialty Crop Weed Management Systems
15.0 Introduction
15.1 What Is Ecologically Based Weed Management in Specialty Crops?
15.2 Unique Challenges for Vegetables and Other Specialty Crops
15.2.1 Weed Competition
15.2.2 Herbicides
15.3 Compatibility of Specialty Crops with Ecologically Based Weed Management
15.3.1 Physical Weed Control
15.3.1.1 Hand Weeding
15.3.1.2 Mulches
15.3.1.3 Cover Crops
15.3.1.4 Mechanical Cultivation
15.3.1.5 Thermal Methods
15.3.2 Cultural Methods of Weed Control in Specialty Crops
15.3.2.1 Prevention and Sanitation
15.3.2.2 Stale Seedbed
15.3.2.3 Subsurface Drip Irrigation
15.3.2.4 Crop Rotation
15.3.2.5 Competition
15.4 Chemical Methods of Weed Control in Specialty Crops
15.5 Conclusions and Suggestions for Future Research
16 The Need of Ecologically Based Weed Management Approaches in Orchard Crops
16.0 Introduction
16.1 Ecologically Based Weed Management Approaches in Fruit Crops Species Grown in Tropical and Subtropical Environments
16.2 Tropical Fruit Crop Species
16.2.1 Pineapple
16.2.2 Bananas
16.2.3 Cocoa
16.3 Subtropical Fruit Crop Species
16.3.1 Citrus
16.4 Ecologically Based Weed Management Approaches in Temperate Fruit Crops Species Growing in Tropical and Subtropical Environments
16.4.1 Peaches (Prunus persica)
16.4.2 Figs (Ficus carica)
16.4.3 Grapevine (Vitis vinifera)
16.5 Conclusions
17 Application of Ecologically Based Weed Management in Pastures
17.0 Introduction
17.1 Ecology of Pasture Systems
17.1.1 Composition of Pastures
17.1.2 Pasture Growth
17.1.3 Influence of Defoliation on Pasture Composition
17.1.4 Weed Infestations in Pastures
17.1.5 Weed Seedbanks in Pastures
17.2 Impacts of Weeds in Pastures
17.2.1 Weed Impacts on Livestock Production
17.2.2 Weed Impacts on Pasture Production
17.3 Weed Management Principles for Pastures
17.3.1 Pasture Monitoring and Weed Prevention
17.3.2 Selection of Suitable Species
17.3.3 Pastures Competing with Weeds
17.3.4 Grazing Management
17.3.5 Manipulating the Soil Seedbank
17.3.6 Removing Problematic Weeds
17.4 Application of Weed Management Principles
17.4.1 Weed Control When Establishing a Pasture
17.4.2 Weed Control in Established Pastures
17.4.3 Target Weed Groups and Suggested Control
17.4.4 Integrated Weed Management
17.4.5 Example of an Integrated Weed Management Strategy
17.5 Future Perspectives
17.6 Conclusions
Index
End User License Agreement
List of Tables
CHAPTER 03
Table 3.1 The impact of climate...
CHAPTER 08
Table 8.1 A sample of weed species...
Table 8.2 A sample of weed species...
Table 8.3 A sample of weed species...
Table 8.4 A sample of weed species...
CHAPTER 09
Table 9.1 Bioherbicide claims...
CHAPTER 11
Table 11.1 Seed retention values...
CHAPTER 12
Table 12.1 Optimal tillage depth...
Table 12.2 The main characteristics...
Table 12.3 Tillage effects on weed...
CHAPTER 13
Table 13.1 Top five vegetable crops...
Table 13.2 Overview of finger and...
Table 13.3 Overview of the most...
CHAPTER 15
Table 15.1 Crop groups specific...
Table 15.2 Cost of hand weeding...
Table 15.3 Weed management costs...
Table 15.4 Effect of selected...
Table 15.5 Area and soil volume...
CHAPTER 16
Table 16.1 Height and diameter...
Table 16.2 Control (%) of ryegrass...
Table 16.3 Number of plants (NP)...
List of Illustrations
CHAPTER 01
Figure 1.1 Examples of the spatial...
CHAPTER 02
Figure 2.1 Ecosystem services...
Figure 2.2 Weed management...
Figure 2.3 Potential drift...
Figure 2.4 Herbicide vapors...
Figure 2.5 Global increase...
CHAPTER 04
Figure 4.1 The relationship...
Figure 4.2 Vertical distribution...
Figure 4.3 Decayed seeds (%) of...
CHAPTER 06
Figure 6.1 Competitive ability...
Figure 6.2 Weed seed distribution...
Figure 6.3 Blackgrass control...
CHAPTER 07
Figure 7.1 Graphic representation...
Figure 7.2 Field margins management...
CHAPTER 08
Figure 8.1 The total number of weed...
Figure 8.2 (a) Leptinotarsa texana...
Figure 8.3 Hypericum perforatum in...
Figure 8.4 (a) Cecidochares connexa...
Figure 8.5 (a) Cyrtobagous salviniae...
CHAPTER 09
Figure 9.1 Sequence of disease and...
Figure 9.2 Weighted summary effect...
Figure 9.3 Schematics of the nanopesticides...
CHAPTER 10
Figure 10.1 A common depiction of the weed...
Figure 10.2 Probability of encountering...
Figure 10.3 An alternative conceptualization...
Figure 10.4 Decayed redroot pigweed...
Figure 10.5 Bare soil between crop...
Figure 10.6 Weeds have established...
Figure 10.7 General principles for...
CHAPTER 11
Figure 11.1 Stages of seed movement...
CHAPTER 13
Figure 13.1 Two of the three cultivation...
Figure 13.2 Overview of conventional...
CHAPTER 15
Figure 15.1 Robovator intelligent...
Figure 15.2 The Bourquin Weed...
Figure 15.3 Two commercial autonomous...
Figure 15.4 Plant Tape automated transplanter...
Figure 15.5 The WeedZapper treating Palmer...
Figure 15.6 Use of irrigation to prepare...
CHAPTER 16
Figure 16.1 Aerial view of trial on critical...
Figure 16.2 Ryegrass infestation before...
Figure 16.3 Species and number of weeds...
Figure 16.4 Importance value index...
Figure 16.5 Total production of fig...
CHAPTER 17
Figure 17.1 Pastures comprise a range...
Figure 17.2 Growth curve of a pasture...
Figure 17.3 A gap in a Cynodon...
Figure 17.4 Even once killed by...
Figure 17.5 Suggested integration...
Guide
Cover
Title Page
Copyright Page
Table of Contents
Preface
List of Contributors
List of Reviewers
Begin Reading
Index
End User License Agreement
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Preface
The necessity of human and environmental protection, along with the evolution of herbicide-resistant weeds, intensifies the need for weed management approaches based on ecological principles. Ecologically based weed management emphasizes the use of ecological principles and practices to minimize weed infestations and crop loses or damages while maintaining and/or enhancing ecosystem health. There are several key components to ecologically based weed management. First, it involves understanding the ecology of the weeds and the ecosystem in which they are growing. This includes factors such as soil type, moisture levels, plant community structure, and disturbance history. By understanding these factors, managers can identify the conditions that favor weed growth and develop strategies to disturb those conditions.
Second, ecologically based weed management seeks to prevent weed infestations from occurring in the first place. This can involve a range of practices, including promoting healthy plant communities, minimizing soil disturbance, using cover crops and other plant-based strategies to suppress weed growth, and implementing early detection and rapid response programs to quickly address new weed outbreaks.
Third, ecologically based weed management emphasizes the use of nonchemical and low-impact control methods whenever possible. This can include manual weed removal, cultural practices such as crop rotation and intercropping, and biological control methods such as the introduction of natural enemies of weeds.
Finally, it recognizes the significance of herbicides or other chemical control methods, although these methods should be used only as an integral part of weed management program and should be applied in a judicious manner to minimize their impact on nontarget species and the surrounding environment. Overall, ecologically based weed management represents a holistic and integrated approach to weed management that balances the needs of crop production with the health and resilience of natural ecosystems.
Ecologically based weed management offers provisional, regulatory, cultural, and supportive services for human wellbeing but also protects the environment. Weed management practices have become closely linked to social and economic, rather than biological, factors, particularly in conventional agriculture, where economic pressures have led to simplification of cropping systems and the replacement of alternate methods of weed management with synthetic chemical options. As a result, the evolution of agroecosystems and weed management strategies, an important part of the agricultural activities, is not progressing in parallel.
This is where this book becomes invaluable. It discusses weed-management practices under the frame of ecological and agro-ecological principles and highlights the benefits and future challenges but also the limitations that the ecologically based weed management approach must overcome. The wide diversity of the topics, along with the important issues in weed science, which are thoroughly discussed in this book, makes each chapter a unique case study.
Chapter 1 discusses the principles of ecologically based weed management, supported by successful case studies. Chapter 2 discusses the fundamental of ecological services and focusses on the services provided when ecological principles are considered in weed control programs, while it refers to specific examples. Another interesting chapter relating ecologically based weed management with climate change is Chapter 3, whereas an extensive reference to nonchemical weed control is made in Chapter 4. Chapter 5, in line with previous chapters, discusses the important role of cultural practices and successfully concludes their positive contribution to ecologically based weed management.
Ecologically based weed management recognizes the significance of herbicides or other chemical control methods in our battle against weeds, although these methods should be used only as a last option and should be applied in a targeted and judicious manner to minimize their impact on nontarget species and the environment. For this reason Chapter 6, which discusses the role of world leading agri-chemical companies such as Syngenta, Bayer, and FMC, on weed management and what they are doing to protect the environment is most interesting. Chapter 7 examines how ecologically based weed management supports pollination, an important constituent for biodiversity conservation and food production within agro-ecosystems. Chapters 8 and 9 address an important, although less investigated, method of weed control – the use of biological agents and biological-based products. Chapter 8 focuses on weed control using arthropods as biological agents and Chapter 9 focuses on plant pathogens and critically assesses their role for weed suppression. It also refers to nanoformulations as a mean to deliver active ingredients for weed suppression. Cover crops, intercrops, and mulches have started to regain interest as effective weed control methods. Chapter 10 extensively analyses the effects and practicalities of these techniques offer in terms of ecologically based weed management.
“One year’s seeding, seven years weeding,” says an old proverb. The focus should be on how to prevent weeds to build a large soil seedbank up, to minimize future problems. Chapter 11 discusses important issues of weed soil seedbank from an ecological perspective with emphasis on soil seedbank management. Chapter 12 further expands our options to reduce soil seedbank and discusses the implications of tillage systems on crop competitiveness, herbicide efficacy, and organic farming. Finally, Chapters 13, 14, 15, 16, and 17 investigate the application of ecologically based weed management on vegetable and specialty crops, row crops, orchards, and pastures. The information provided in these chapters is exceptional and can be used for a wide range of cropping and farming systems.
This book will be an invaluable source of information for scholars, growers, consultants, researchers, and other stakeholders dealing with agronomic, horticultural, and grassland-based production systems. The uniqueness of this book comes from the coverage of the most suitable ecologically based weed management practices that secure ecosystem services to humans and the environment. It reviews the available information critically and suggests solutions that are not merely feasible but also optimal. Readers will gain an in-depth knowledge on ecosystems services and weed practices. They will also be able to learn the principles of ecologically based weed control management, which are needed now more than ever.
Despite the great effort that authors, editors, and reviewers have invested in this work, mistakes may have been made. We would like to ask readers to inform us of any mistakes or omissions they find, as well as suggestions for future improvements by mailing us at the following email addresses, with “Ecologically Based Weed Management. Concepts, Challenges, and Limitations” in the subject line.
Nicholas E. Korres, PhD
Ilias S. Travlos, PhD
Thomas K. Gitsopoulos, PhD
List of Contributors
Ignacio AspiazúDepartment of Agricultural SciencesState University of Montes ClarosJanaúba, BrazilSusan M. BoyetchkoDeceased. Formerly Research ScientistSaskatoon Research and Development CentreAgriculture and Agri-Food CanadaUniversity of SaskatchewanSaskatoon, Canada
Parminder ChahalField Development RepresentativeFMC CorporationUniversity of NebraskaLincoln, Nebraska, USA
Raghavan CharudattanPresident and CEO, BioProdex, Inc.Emeritus Professor, University of Florida,Gainesville, Florida, USA
Bhagirath S. ChauhanQueensland Alliance for Agriculture and FoodInnovation (QAAFI) and School of Agriculture andFood Sciences (SAFS)The University of QueenslandGatton, Queensland, Australia
Germani ConcençoBrazilian Agricultural Research CorporationCapão do Leão, Brazil
Michael D. DayDepartment of Agriculture and FisheriesBrisbane, Queensland, Australia
Steve FennimoreDepartment of Plant SciencesUniversity of California–DavisSt. Salinas, California, USA
Evander Alves FerreiraInstitute of Agricultural SciencesFederal University of Minas GeraisMontes Claros, Brazil
Karla L. GageSchool of Agricultural Sciences/School of BiologicalSciencesSouthern Illinois University–CarbondaleCarbondale, Illinois, USA
Leandro GalonUniversidade Federal da Fronteira SulChapecó, SC, Brazil
Ioannis GazoulisAgricultural University of AthensAthens, Greece
Roland GerhardsDepartment of Weed Sciences, Institute of PhytomedicineUniversity of HohenheimStuttgart, Germany
Clevison Luiz GiacobboUniversidade Federal da Fronteira SulChapecó, SC, Brazil
Thomas GitsopoulosHAO-Demeter, Institute of Plant Breeding and GeneticResourcesThermi – Thessaloniki, Greece
Katherine M. JenningsDepartment of Horticultural Science, North CarolinaState UniversityRaleigh, USA
Panagiotis KanatasUniversity of Patras (Teaching Staff P.D. 407/80)Mesolonghi, Greece
Filitsa KaramaounaScientific Directorate of Pesticides Control andPhytopharmacyBenaki Phytopathological InstituteKifissia, Greece
Vaya KatiLaboratory of Agronomy, School of AgricultureFaculty of Agriculture, Forestry and NaturalEnvironmentAristotle University of Thessaloniki, Thessaloniki, GreeceandScientific Directorate of Pesticides Control andPhytopharmacyBenaki Phytopathological InstituteKifissia, Greece
Nicholas E. KorresDepartment of AgricultureUniversity of IoanninaKostakii, Arta, Greece
Stevan Z. KnezevicProfessor of Integrated Weed ManagementDepartment of Agronomy and Horticulture,University of Nebraska-Lincoln, Lincoln,Nebraska, USA
Eduardo S. Leguizamon E.SRosario National UniversityRosario, Republic of Argentina
Natalie P. LounsburyDepartment of Agriculture, Nutrition, andFood SystemsCollege of Life Sciences and AgricultureUniversity of New Hampshire, Durham, USA
Jonathan W. McLachlanSchool of Environmental and Rural ScienceUniversity of New EnglandArmidale, Australia
Victor Martins MaiaDepartment of Agricultural SciencesState University of Montes ClarosJanaúba, Brazil
Miriam MesselhäuserDepartment of Weed Sciences, Institute ofPhytomedicineUniversity of HohenheimStuttgart, Germany
Andrea Monroy-BorregoDepartment of NanoEngineeringUniversity of California–San DiegoSan Diego, California, USA
Adusumilli Narayana RaoConsultant ScientistJubilee Hills, Hyderabad, India
Georg NaruhnDepartment of Weed Sciences, Institute of PhytomedicineUniversity of HohenheimStuttgart, Germany
Iraj NosrattiDepartment of Plant Production and GeneticsFaculty of Agriculture, Razi UniversityKermanshah, Iran
Samuel A. PalmerDepartment of Natural Resources and the EnvironmentUniversity of New Hampshire, Durham, USA
Gerassimos PeteinatosCentre for Automation and Robotics (CSIC)Madrid, SpainandHellenic Agricultural Organization – DIMITRADepartment of Agricultural Engineering, Soil and WaterResearch InstituteAthens, Greece
David ReiserDepartment of Technology in Crop ProductionInstitute of Agricultural EngineeringUniversity of Hohenheim,Stuttgart, Germany
Erin N. RosskopfResearch Microbiologist, USDA-ARSU.S. Horticultural Research LaboratoryFort Pierce, Florida, USA
Aritz Royo-EsnalDepartment of Agricultural and Forest Science andEngineeringETSEAFIV-Agrotecnio Centre, Universitat de LleidaLleida, Spain
Lauren M. Schwartz-LazaroBlue River TechnologySunnyvale, California, USA
Matthias SchumacherDepartment of Weed Sciences, Institute of PhytomedicineUniversity of HohenheimStuttgart, Germany
Brian M. SindelSchool of Environmental and Rural ScienceUniversity of New EnglandArmidale, Australia
Alexandre Ferreira da SilvaBrazilian Agricultural Research CorporationCapão do Leão, Brazil
Milena SimićMaize Research Institute “Zemun Polje”Belgrade–Zemun, Serbia
Richard G. SmithDepartment of Natural Resources and the EnvironmentUniversity of New Hampshire, Durham, USA
Michael SpaethDepartment of Weed Sciences, Institute of PhytomedicineUniversity of HohenheimStuttgart, Germany
George Andrade SodréState University of Santa Cruz,Neighborhood Salobrinho, BA, Brazil
Nicole F. SteinmetzInstitute of Engineering in MedicineUniversity of California–San DiegoSan Diego, California, USADepartment of Radiology,Moores Cancer Center, University of California-San Diego,La Jolla, USA
Joel TorraDepartment of Agricultural and Forest Science andEngineeringETSEAFIV-Agrotecnio Centre, Universitat de LleidaLleida, Spain
Ilias TravlosAgricultural University of AthensAthens, Greece
Vijay K. VaranasiBayer Crop ScienceSt. Louis, Missouri, USA
Ioannis VasilakoglouDepartment of Agronomy – AgrotechnologyUniversity of ThessalyThessaly, Greece
Vasileios P. VasileiadisHead of Regenerative Agriculture, Europe, Africa, andMiddle EastSyngenta Crop ProtectionAthens, Greece
Kaydene T. WilliamsU.S. Horticultural Research LaboratoryFort Pierce, FLand University of Florida-Gulf Coast Research andEducation CenterWimauma, Florida, USA
Rachel L. WinstonMIA ConsultingShelley, Idaho, USA
Arne B. R. WittCABINairobi, Kenya
Rosa WittyDepartment of Weed Sciences, Institute of PhytomedicineUniversity of HohenheimStuttgart, Germany
List of Reviewers
Albert T. Adjesiwor Assistant Professor and Extension Specialist, Department of Plant Sciences, University of Idaho, Kimberly Research & Extension Center, Kimberly, USA.
Warwick Badgery Research Leader Rangelands and Tropical Pastures, NSW Department of Primary Industries, Australia.
Barbara Baraibar Researcher, University of Lleida, Spain.
Lammert Bastiaans Professor, Wageningen University, Centre for Crop Systems Analysis, The Netherlands.
Milan Brankov Researchers, Maize Research Institute “Zemun Polje”, Serbia, Ioannis Gazoulis, Research Assistant, Agricultural University of Athens, Greece.
Mehmet Nedim Dogan Professor, Adnan Menderes University, Turkey
Stephen Duke Adjunct Research Professor, Thad Cochran Research Center, Mississippi State University, USA.
Eric Gallandt Professor, Weed Ecology and Management, University of Maine, USA.
Thomas Gitsopoulos Senior Researcher, Institute of Plant Breeding and Genetic Resources, ELGO-DIMITRA, Thessaloniki, Greece.
Kerry Harrington Associate Professor, School of Agriculture and Environment, Massey University, New Zealand.
Panagiotis Kanatas Teaching Staff, University of Patras, Greece.
Vaya Kati Assistant Professor, School of Agriculture, Faculty of Agriculture, Forestry and Natural Environment, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Ioannis Kazoulis Associate Professor, Agricultural University of Athens, Greece
Khawar Jabran Associate Professor, Plant Production & Technologies Department, Nigde Omer Halisdemir University, Nigde, Turkey.
Nicholas E. Korres Associate Professor, Dept. of Agriculture, School of Agriculture, University of Ioannina, Kostakii, Arta, Greece.
Spyridon Mantzoukas Research Fellow, Department of Agriculture, University of Ioannina, Ioannina, Arta, Greece.
Maor Matzrafi Senior Researcher, Volcani Institute, Newe-Ya’ar Research Center, Israel
Fabian Menalled Professor, Land Resources and Environmental Sciences, Montana State University, USA.
Husrev Mennan Professor, Ondokuz Mayıs University, Agriculture Faculty, Department of Plant Protection, Samsun, Turkey.
Mario Luiz Ribeiro Mesquita Professor, Departamento De Ciencias Agrarias – Bacabal, Brazil.
Sheeja K. Raj Assistant Professor (Agronomy), Department of Organic Agriculture, Kerala Agricultural University, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, India.
Ilias Travlos Associate Professor, Agricultural University of Athens, Greece.
N. T. Yaduraju Formerly: Director, ICAR - Directorate of Weed Research, Jabalpur, National Coordinator, National Agriculture Innovation Project (ICAR) and Principal Scientist ICT4D, ICRISAT, Hyderabad, India.
Ioannis Vasilakoglou Professor, Department of Agriculture-Agrotechnology, University of Thessaly, Larissa, Greece.
Costas Zachariades Senior Researcher, Agricultural Research Council, South Africa, ARC, Plant Protection Research Institute, South Africa.
1 Ecologically Based Weed Management (EbWM)Enabling and Reinforcing the Approach
Leguizamon Eduardo S.1,*, Royo-Esnal Aritz2, and Torra Joel2
1 Cajaraville, Rosario, República Argentina2 Department of Agricultural and Forest Science and Engineering, ETSEAFIV-Agrotecnio-CERCA Centre, Universitat de Lleida. Alcalde-Rovira Roure, Lleida, Spain * Corresponding author
1.0 Introduction
Managing food production systems on a sustainable basis is one of the most critical challenges for the future of humanity. Being fundamentally dependent on the world’s atmosphere, soils, water, and genetic resources, these systems provide the most essential ecosystem services on the planet. They are also the largest global consumers of land and water, threats to biodiversity through habitat change, and significant sources of air and water pollution in several regions on Earth (Naylor 2008).
The increase in the world population is necessarily associated with a greater demand for food produced by crops, among other approaches (e.g. reducing food wastes or synthetic food). Currently, there are limited possibilities of achieving crops with superior yields, and incorporating new territories into agriculture is not a realistic option. Under these grounds, it is clear that one factor that favors the increase in crop productivity is the management of species considered pests. In this context, weeds are one of the most important biotic constraints.
During the last 70 years, intensive measures have been taken for crop protection against pests through the widespread use of chemical pesticides in order to reduce the loss of agricultural yield. Although mainly chemical-based, crop protection practices have reduced the overall potential losses of 50% to actual losses of about 30%, with crop losses due to pests still varying from 14% to 35% depending on the considered crop and country (Oerke 2006). Consequences of this massive-intensive chemical use in the agroecosystems are increasingly studied as concerns rocketed all over the world.
Integrated pest management (IPM) was proposed 70 years ago by Stern et al. (1959), who outlined a simple but sophisticated idea of pest control in order to manage insect pests while reducing reliance on synthetic pesticides. Briefly, IPM is based on four elements:
Knowledge of the thresholds to determine the need for control
Necessary population sampling to determine critical densities (economic damage)
The biological control capacity in the system
Use of insecticides or selective methods compatible to biological control enhancement (Thill et al. 1991)
Later on, Swanton and Weise (1991) after other precursors, proposed the use of integrated weed management (IWM) as a similar approach for weed management in agroecosystems. IWM was then inspired by IPM, as a long-term management strategy that uses a combination of strategies to reduce the population size of weeds to a tolerable level, being economically affordable and also as a tool to reduce undesired environmental effects of herbicides. However, in most crop production systems, generalized recommendations include just a combination of management tactics (cultural + chemical). After more than 30 years, IWM remains in its infancy, since the implementation of IWM has been poor, with little evidence of its sustainability (e.g. reductions in herbicide use). Moreover, nonchemical methods (mechanical) are often adopted as a means of compensating for reduced herbicide efficacy, due to increasing resistance, rather than as alternatives to herbicides. Reluctance to adopt nonchemical methods may be due not only to a lack of knowledge, but also to a lack of farmer motivation and action and/or risk aversion (Moss 2018). Justifiably, herbicides are often seen as the easiest and still most effective option since their convenience outweighs the increased complexity, costs and management time associated with nonchemical alternatives.
To bring numbers to the statements already said, surveys recently made by crop advisors in Argentina (Satorre 2015) within high technology agricultural entreprises concerning the weed problems they faced in the last decade, revealed the following:
There is great concern about weeds, considered the main adversity, especially in summer crops.
Weed management technologies used in the last decades have only been based on herbicides and, surprisingly, they are still led by glyphosate.
Increasing number of species exhibit a range of herbicide tolerant / resistant responses.
It is only recently that some farmers (less than 10% acreage) began to include cultural practices (such as cover crops).
There is a lack of incentives for application of IWM practices and/or pesticides reduction programs.
70% of summer crops are planted on short-term leased land, where actions are mostly oriented toward annual productivity, neglecting possible future problems such as contamination or the appearance of herbicide resistant weeds.
Thus, although IWM is frequently advertised/proclaimed as a dominant concept associated to sustainability, the difficulty of evaluating the benefits derived from alternative approaches, ignorance, and/or a low use of available knowledge of weed biology present a severe barrier to changes: up to the present time, a majority of the farmers have failed in a massive implementation of IWM.
Similar results emerged from a recent survey made in the cornbelt from the USA. To elucidate the causes or barriers that prevent huge adoption of IWM, Al-Mamun (2018) identified “failures of institutional context declining government policies, counteracted by multinational private companies as main actors.” A further contribution (Wilson et al. 2009a) states that “agrochemical supplier companies impose the massive use of their products through business marketing strategies, preventing producers from being oriented in the use of more sustainable practices,” and that a key aspect is that “crop advisors should manage to transmit sufficient trust toward the farmers to be able to address the real problem in a clear and concrete way.” For this, it is necessary to create a strong link between the different actors through intensive two-way communication and a greater understanding of the way in which producers perceive this problem (Wilson et al. 2009b). A further issue that should be revised is stewardship programs systematically launched and advertised by the agrochemical industry and also by plant protection sellers and distributors in general, with a rather shallow view in relation to the principles of IWM and advanced available knowledge.
An example on a low-profile marketing campaign was that made about 30 years ago when Roundup-Ready soybeans were launched in Argentina. Adverts in media and in rural roads, boosted the use of the simplest solution to tackle weed problems: just glyphosate. Think of glyphosate in the crops – first in soybeans, then in corn, and later on in cotton and others – plus glyphosate in the fallow. In fact, the tremendous success of direct drilling in Argentina was only possible when two hard technological bottlenecks were overcome: how to place seeds in an undisturbed soil by mouldboard-plough + harrowing (using newly designed planters) and how to get rid of weeds without mechanical tactics (using a novel and very effective herbicide: glyphosate).
Not only companies but also advisors and educators may fail to promote IWM within the frame of farmers’ experience and belief structure. Targeted communication efforts that address key misperceptions, and highlight the cost-effective nature of integrated approaches may increase adoption of IWM and ultimately increase sustainability of the agroecosystem. Unfortunately, IWM systems have been perceived as unreliable, resulting in increased risk of weed control failure. The acceptance of IWM by growers will depend on their risk perception of management, individual management capability and environmental interactions that will influence the economic viability of the crop system. The adoption of IWM is usually hindered by the fact that chemical means are often growers’ first and only choice, as synthetic herbicides are perceived as an effective, rapid and cost-effective solution for weed management. However, the consequences of intensive pesticide usage in agriculture are now quite well known and fortunately widely and progressively studied, being the increasingly widespread herbicide-resistant weed biotypes as the most striking example of the unsustainability of current plant protection strategies.
1.1 Basis for a Sucessful Ecologically Based Weed Management Approach
In 2008, Bastiaans et al. reflected on the possibilities and limitations of ecological approaches in weed control practices, highlighting the need for research in order to provide clear insight in effectiveness and applicability of the utilization of ecological knowledge translated into practical strategies of weed management. If we do agree that the maintenance of resilience and diversity are key issues for the agriculture to be sustainable (and even more under the intensification process already started), then we should address for a reinforced and enlarged ecologically based weed management (EbWM) definition, backed up by complementary major related disciplines. It must be pointed out that ecology provides the theoretical basis for weed science, much as physics provides a theoretical basis for engineering and biology the theoretical basis for medicine (Liebman et al. 2001). Although much research has been focused on the ecological relationships of weeds within agroecosystems in recent years, substantial gaps in knowledge relevant to weed management still exist, since weed management strategies must include multiple points of intervention in their life cycles (Liebman and Gallandt 1997).
Production models successfully developed in the last decades in various regions of Europe, America, and elsewhere, clearly demonstrate that the coexistence of production systems conducted under different and conceptual views is possible. What is clear is that goverment policies should ensure the success of each of them, whether implemented by individual producers, by organizations, by cooperatives, or by companies, designing provisions and control and promotion mechanisms with policies that allow their free implementation within a framework of respect and sustainability in the broadest sense. Such is the case of the European standards for the creation and use of transgenic varieties, of organic productions and even more, of crop productions rescueing ancestral varieties.
Box 1 Population Biology of Plants
A fundamental issue and the core of EbWM is the consideration that not only the crop but also the weeds are organized at the level of the population. In plants, growth is modular: the “sections” or “modules” (the phytomer) are repeated over and over again, allowing the increase in size and biomass: plants (crops and weeds) are modular organisms. Growth based on repeated modular structures (the phytomer) provides great plasticity and has a profound significance in the competitive capacity, fertility, propagation, and persistence of a given genotype. Plastic responses should be taken into account when studying and modeling weed-crop interactions and also when evaluating the effects of management factors affecting density (e.g. herbicides, competition with the crop, interactions with cover crops). From the population dynamics point of view, each state that defines a weed life history begins with the germination of the seed and ends with the production of new seeds by adult plants, their subsequent dispersal and posterior seedbank incorporation. The number of variations of any stage in the life cycle of a plant (e.g. seedlings, plants, seeds) can be traced using demographic tools. The responses of vital rates in relation to the environment, determine the dynamics of populations in an ecological time and the evolution of life histories, in an evolutionary time. When calculating vital rates during the life cycle, demographics take into account both the dynamics and the structure of populations. The goal of a successful weed management program is to reduce the rate of population change, that is, lambda (λ) calculated as the ratio of the next to the current population size.
from Harper, J.L. 1979
Simultaneously, weed scientists should shift their focus from trying to create prescriptive ways to manage weeds to developing ways for farmers to gain site-specific knowledge that will allow them to decrease the uncertainty of greater reliance on natural weed population regulating mechanisms. Most “weed problems” are really “people problems” evolved from poor land management and a deep lack of ecological insight.
1.2 Enabling and Reinforcing EbWM Principles in All Crop Production Systems
Kleijn et al. (2019) warn that large-scale adoption of ecological intensification requires stronger evidence than is currently available. Future research should therefore not only address ecological, agronomic, and economic aspects of ecological intensification but also the sociological aspects. To contribute to this goal, knowledge may contribute to reinforce and spread the application of ecological principles in a variety of crop systems, including those who depend on herbicide technology.
It is envisaged that the following six pillars can contribute to reach the objectives for an extended and deeper usage of EbWM principles in any kind of crop system.
1.2.1 Systems Approach
“Rotation of crops…is the most effective means yet devised for keeping land free of weeds. No other method of weed control, mechanical, chemical, or biological, is so economical or so easily practiced as a well-arranged sequence of tillage and cropping.”
C.E.R. Leighty 1938. Yearbook of Agriculture. USA.
EbWM should be the core of weed management in any cropping system, whatever it is intensive, extensive, organic or industrial. Gage et al. (2019) define the concept of Systems Approach as managing weeds by combining practice and knowledge with the goals of increasing yield and minimizing economic loss, minimizing risks to human health and the environment, and reducing energy requirements and off-target impacts. The reliance on herbicides in modern cropping systems should shift the management focus from requiring intimate knowledge of biology, ecology, and ecological systems to herbicide chemistry, mixtures, and rotations, application technology, and herbicide-tolerant crop traits. Prevention of spread, seedbank management, crop rotations, tillage, cover crops, competitive cultivars, or biological weed control all require to fill identification of knowledge gaps where research advancements may be possible. Then, an ecological systems approach may provide improved stewardship of new herbicide technologies and reduce herbicide resistance evolution through diversification of selection pressures. Interestingly, several authors include the need of a careful planning and setting of experiments lay-out according to the objectives, focusing on scale considerations.
A total system approach may contribute to the necessary reduction of the heavy use of pesticides by using the knowledge provided by ecology and related disciplines. Lewis et al. (1997) proposed a diagram to illustrate the necessary shift to a total system approach to pest management through a greater use of inherent strengths based on a good understanding of interactions within an ecosystem while using therapeutics as backups: an upside-down pyramid reflected the unstable conditions under heavy reliance on pesticides, and an upright pyramid reflected sustainable qualities of a total system strategy.
1.2.2 Increased Biodiversity in the System
Several experiments have been made with this perception in the last 20 years. For example, Bastiaans et al. (2007) focused their research on enhancing the diversity to manage weeds in very different cropping systems in the Netherlands (e.g horticultural) by intercropping slow growing vegetables such as onion, carrot and leek, and sequential use of cover crops when the main crop is absent (stubble).
The complementary exploitation of resources by combined extensive crops has also been studied during three consecutive years in soybean-corn strips by Verdelli et al. (2012). These authors demonstrated that corn yield in the strips significantly increased as compared to that in the monocultures due to increased yields in corn plants of the border rows of the strips, which was highly correlated to an increased radiation interception, allowing higher crop growth rates at critical crop stages. Conversely, soybean yields in the strips were lower than that in the monocultures; however, the strip-crops system overyielded monocultures. Authors emphasize that the use of more appropriate genotypes may contribute to increase the differences and then ease the spread of this technique in actual massive monocultured agricultural systems of Argentina.
Getting back to experimental design considerations, Petit et al. (2018) appoint that further advances in the understanding of biodiversity-based options and their performance for weed biocontrol require farm-scale experimental trials. In this sense, the evaluation of the influence of herbicide-resistant crops on biodiversity (e.g invertebrates and vegetation of field margins) made by Roy et al. (2003) across English countryside fields, may be a good experimental and theoretical vision as they, early on, highlighted the importance of butterflies evaluation as key indicator species in the study of agroecosystems. In the same line, Alignier et al. (2020) have found that crop heterogeneity increases within-field plant diversity.
Petit et al. (2018) have studied several biodiversity-based options for arable weed management since they questioned that IWM currently recommends agronomic practices for weed control, but it does not integrate the use of biodiversity-based options that enhance the biological regulation of weeds. In their contribution, they alert and describe existing knowledge related to three potentially beneficial interactions, crop–weed competition, weed seed predation, and weed interactions with pathogenic fungi. They found that promoting cropped plant–weed competition by manipulating cropped cover could greatly contribute to weed reduction; that weed seed predation by invertebrates may significantly reduce weed emergence; and that a wide range of fungi may be pathogenic to various stages of weed development. Again, they warn about the necessary requirement of farm-scale experimental trials. Hails (2002) also points out the careful design of key elements of long monitoring biodiversity.
In a very interesting approach, Petit et al. (2015) use weeds as a model for exploring management options relying on the principle of ecological intensification in 55 experimental farm fields. The authors use weeds because they can cause severe crop losses, contribute to farmland functional biodiversity and are strongly associated with the generic issue of pesticide use. They monitor the impacts of herbicide reduction following a causal framework starting with less herbicide inputs triggering changes in (i) the management options required to control weeds, (ii) the weed communities and functions they provide, and (iii) the overall performance and sustainability of the implemented land management options. Interestingly, the reduction of herbicide use was not antagonistic with crop production, provided that alternative practices are put into place. Outcomes suggest that sustainable management could possibly be achieved through changes in weed management, along a pathway starting with herbicide reduction. Humans should increase biodiversity in human-dominated landscapes. Science provides robust foundations for predictions on human land-use trends and species-area relationships.
1.2.3 Inclusion of the Spatial Scale in the System: From the Field to the Landscape
The intensification of agricultural practices and the increase of area under agricultural production, which was accompanied by a destruction of perennial habitats, made agriculture one of the main causes of biodiversity losses. Though annual arable weed populations outlast with their seedbank, they can also benefit from the seed rain from the surrounding landscape. Thus, it is not only important to support the survival conditions within the fields (e.g. by extensive management), but also consider the structure of the landscape (Solé-Senan et al. 2014). The role of arable weeds in cereal aphid-natural enemies’ interactions was analyzed in Roschewitz’s PhD thesis (2005).
The decision-making regarding weed management in agricultural systems is influenced by a wide range of factors that operate at variable spatio-temporal scales. In 1997, Rabbinge proposed a simple scheme combining the two leading factors in the ecological consideration of living organisms of the agroecosystem (Figure 1.1): space (x-axis) and time (y-axis). It helps farmers figure out where to focus their activities and how to envisage the issues and dynamics concerning the time scale (e.g. a weed seed in the soil) or the space scale (the movement of a seed by the wind a long way from the mother plant). Interestingly, the author superimposed succesive demographic, geographic, and ecological levels where the experiments and research may be located.
Figure 1.1 Examples of the spatial and temporal scale for investigations of hierarchical levels within natural (light colored) and agricultural systems (dark colored) (Dalgaard et al. 2003).
EbWM grounded on ecological systems approach may maximize yield and minimize risks to farmers’ health and to the environment, while reducing energy requirements and additional effects (“externalities”) such as the maintenance of biodiversity by managing borders and margins. Thus, tactics used should modulate the processes strongly influencing weed population size (e.g. seedbank management, fertility management, postdispersal), crop rotation, tillage, service crops, and the competitive ability of crop cultivars. Herbicide evaluation should consider not only the efficacy but also the fecundity of the uncontrolled population, consequently affecting the seedbank. The scale should be strongly replaced, shifting from “weed management of the field” to “management of weeds in the production systems of the region.” Under this broad conception, we may find healthy agroecosystems, where traditional low-input activities are performed, with diverse weed communities that contribute to resilience. For example, several studies identify a wide range of taxa, including birds and mammals, invertebrates, and arable flora that benefit from organic management compared to conventional agriculture (Hole et al. 2005). In other cases, plant species richness can change with altitude because less intensified agriculture is associated with higher elevations, as was found in Central Europe (Pysek et al. 2005) and Spain (Cirujeda et al. 2011). First, these agroecosystems should be preserved, of course, and second, there are very important principles that can be learned from them to fuel the application of EbWM tools.
There are other agroecosystems where weed diversity has been reduced to very invasive species (fast weeds) often resistant to herbicides, and where arable less-competitive plants (slow weeds) have disappeared. In these agroecosystems, applying EbWM is more difficult. The high densities and high competitive capacity of these weeds require a first step that might take some years of effective IWM strategy applications to be able to reduce their populations trying to deplete their soil seedbank. Once these populations have been reduced (not eradicated), the ecological niche is receptive to establishing other species populations that could be managed with EbWM principles.
There is then a range of agroecological approaches with variable performances, but win-win scenarios are demonstrated, where both environment and profitability can be reinforced. Among them, sustainable intensification or agroecological intensification (AEI) stands out. Here, intensification involves improvement of farm and system performance through the implementation of agroecological principles, rather than intervention (Elliot et al. 2013).
Finally, it must be pointed out, as MacLaren et al. (2020) did, that the design and implementation of EbWM strategies at agroecosystem level is complex, because an understanding of the ecological interactions is required, as well as the theoretically relevant practices that could match the different environments and farming systems to achieve sustainable, healthy, and environmentally friendly food production systems. Moreover, the competition capacity of a weed community against crops is affected by its composition and diversity, as well as its capacity to support biodiversity and provide ecosystem services (MacLaren et al. 2020). Thus, in each situation (field-crop-landscape) knowledge of the type of weeds present and their relative abundance, in addition to total weed density or biomass, is needed in order to apply effective EbWM strategies.
1.2.4 Significant Improvement in the Objectives of the Crop Breeding Programs
Lamichhane et al. (2017) advocate a need for suitable breeding approaches to boost a more sustainable management since European farmers do not have access to a sufficient number and diversity of crop species/varieties. This prevents them from designing more resilient cropping systems to abiotic and biotic stresses. These authors propose a new breeding paradigm called breeding for integrated pest management (IPM), which could easily be extended to EbWM with an ultimate goal of reducing reliance on conventional pesticides.
Organic farming systems are under the same restrictions (Lammerts et al. 2002): these systems aim at resilience and buffering capacity in the farm ecosystem by stimulating internal self-regulation through functional biodiversity in and above the soil, instead of external regulation through chemical protectants. However, organic farmers largely depend on varieties supplied by conventional plant breeders and developed for farming systems in which artificial fertilizers and agrochemicals are widely used. Until now, many of the desired crop traits have not received enough priority in conventional breeding programs. The proposed organic crop ideotypes may benefit not only from organic farming systems but also from conventional systems that move away from high inputs of nutrients and chemical pesticides.
