**2. Importance of bioherbicides**

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.

*Epicoccum, Exserohilum, Fusarium, Gloeocercospora, Microsphaeropsis, Mycoleptodiscus, Myrothecium, Phoma, Phomopsis, Plectosporium, Pseudolagarobasidium, Pseudomonas, Puccinia, Pyricularia, Pythium, Sclerotinia, Serratia, Stagonospora, Streptomycetes, Trichoderma, Verticillium,* and *Xanthomonas* species and also several plant extracts have been recorded as bioherbicides [12].

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Introductory Chapter: Need of Bioherbicide for Weed Control

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Even though numerous plant products and microbes have been successfully showing the positive results against weeds in field trialed, only a few (one plant extract, three bacteria, and nine fungi) of them are commercially available in current markets [8]. Hoagland [13] demonstrated that the crop plants especially tomato produces allelochemicals such as tomatine and tomatidine, which prevent the growth of weeds and pathogenic fungi. Recently, the researchers are interested to know the bioherbicide compounds by extracting DNA fragments obtained from the soil and cloning the genes in vectors to produce phytotoxic compounds [14]. The mode of action of bioherbicide is not well elucidated, but a few studies revealed that the toxic metabolites from the microbes or plant-based products prevent the population of weeds by affecting cell division, pigment synthesis, nutrient uptake, plant growth promoting regulators, antioxidants, stress-mediated hormones, and other metabolites [13]. In organic farming, the bioherbicide approach is used to avoid herbicide resistance and increase crop yield [15]. In this book, the importance of bioherbicides and integrated management of weed control with tillage, mulching, and other eco-friendly methods are enlightened.
