Preface

Weed populations in agriculture are a major cause of yield loss. Conventionally, crop rota‐ tion and tillage practices limit the number of weed flora. Biological agents are used as bio‐ herbicides against weeds, which are an alternative to chemical herbicides. Several studies reveal that plant extracts, bacteria, fungi and their products effectively control weed seed germination and growth.

*Biological Approaches for Controlling Weeds* is intended to offer current knowledge on biological methods to control weed populations. It includes six chapters. The introductory chapter presents the hazardous effects of chemical herbicides and the need of biological agents to control weed populations. Chapter 2 describes the overall biological approach of weed con‐ trol, including principles and procedures for biological weed control, success rate of biologi‐ cal agents and making the choice of which agents to use. The conventional way of weed control by using the tillage system is explained in Chapter 3. It shows the importance of till‐ age types, seed bed preparation and weed removal. Chapter 4 reveals that a genetic differ‐ ence between weed competition and allelopathy is evidenced with canola populations. Plant extracts and their essential oils suppress weed growth and their phytotoxic activities are fo‐ cused on in Chapter 5. In Chapter 6, the role of mycoherbicides on weed control, production of fungal spores, propagules, mass cultivation, storage and their utilization are discussed.

The information provided in this book will be useful for researchers, students and farmers to understand the importance of bioherbicides. All the authors are gratefully acknowledged for their efforts in writing the chapters.

#### **Dr. Ramalingam Radhakrishnan**

Assistant Professor Department of Microbiology Karpagam Academy of Higher Education Eachanari, Coimbatore, India

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: Need of Bioherbicide for Weed**

**Introductory Chapter: Need of Bioherbicide for Weed** 

Food production is affected by climatic changes and environmental pollutions. The growth and yield of crop plants are significantly declined due to the effect of weed (a plant considered unwanted in a particular location) growth in farming fields. Weeds are strong competitors against crops to the absorption of water and nutrition from the soil, and also occupy more soil area, which result to suppress the crop growth [1, 2]. The integrated approach of weed control management (including tillage, mechanical way of weed removal, and crop rotation) can able to effectively decrease the weed growth [3–5]. The application of chemical-based herbicides, that is, 2,4-dichlorophenoxyacetic acid (2,4-D), glyphosate, and dicamba suppress the germination and growth of weeds, but the prolonged application of those chemicals could not effectively control the weeds and causes to develop the resistant weed germplasms and also pollutes the environment [6]. In addition, Kim et al. [7] reported that 32% of food products in Korea are unsuitable for consumption due to higher accumulation of pesticides. Recently, several biological organisms or their extracts are utilized to integrate weed control strategies [8].

Bioherbicides are either living organisms or the natural metabolites that have the ability to control weed populations without harming the environment [9, 10]. The numbers of bacterial and fungal species demonstrate their host-specific or nonspecific bioherbicide activities against susceptible weed populations [9]. In 1980, the commercial form of bioherbicide was first introduced in the USA, Canada, Ukraine, and Europe [8, 10, 11]. The microbial agents such as *Alternaria, Bacillus, Chondrostereum, Colletotrichum, Curvularia, Dactylaria, Diaporthe, Drechslera, Enterobacter,*

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.77958

**Control**

**1. Introduction**

**Control**

Ramalingam Radhakrishnan

http://dx.doi.org/10.5772/intechopen.77958

**2. Importance of bioherbicides**

Additional information is available at the end of the chapter

Ramalingam RadhakrishnanAdditional information is available at the end of the chapter

#### **Introductory Chapter: Need of Bioherbicide for Weed Control Introductory Chapter: Need of Bioherbicide for Weed Control**

DOI: 10.5772/intechopen.77958
