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Preface
The ultimate aim of crop husbandry is to cultivate crops and obtain maximum returns according to their genetic potential. Pathogenic microorganisms stand in the way of crops attaining their full growth and maturity. Some plant pathogens, as a result of infection of the host plant may cause death of a part or the entire plant and cause total loss, while some others affect some parts of the plant resulting in reduction of yield. Some pathogens may affect the stored produce and cause spoilage. So, it becomes imminent that plant pathogens have to be controlled by adopting appropriate control measures so as to minimize the losses and maximize the yield.
The causative agents of diseases in plants include pathogenic microorganisms, such as fungi, bacteria, viruses, mycoplasma, protozoa and nematodes; phanerogamic parasites, algae and lichens of the Plant Kingdom; abiotic agents or unfavorable environmental factors, such as deficiency due to lack of certain macro or micro nutrients or toxicity due to excess of certain macro and micro nutrients; moisture, light or heat stress, as well as the presence of some toxic chemicals in the air, soil or water.
Plant pathology deals with the study of plant diseases caused by various pathogenic agents and environmental factors; the mechanisms by which these agents or factors induce diseases in plants; occurrence and mode of spread of the diseases and the methods of preventing or controlling them, thereby reduce the damage and consequent loss caused by them. As a separate field of Biological Science, Plant Pathology helps to enhance our knowledge about plant diseases, at the same time it tends to develop methods, equipments and materials through which plant diseases can be avoided or controlled.
In an ecological community, the majority of living organisms are plants. Plants have the ability to convert solar energy into chemical energy through the process of photosynthesis and this chemical energy is stored in the form of carbohydrates, proteins and fats in the plant cells. All vertebrates including humans, animals etc. and invertebrates, such as insects, nematodes etc. depend entirely on these plant materials for their survival and existence.
It has been established that microorganisms were present on this earth several thousands of years before humans and plants came into existence and had intruded into the world of microorganisms. These microorganisms, which had been living entirely on the organic matter for their sustenance, had gradually changed their mode of life and had become parasites on plants. These parasites, which cause various types of plant diseases, are known as plant pathogens.
Infection by plant pathogens invariably exhibits certain specific abnormalities in the host plants called disease symptoms. Each and every pathogenic microorganism produces quite different and distinct symptoms. These symptoms may be visible to the naked eye or in some cases may not be visible externally. From such characteristic symptoms, most of the diseases, such as leaf spots, blights, rusts, smuts, wilts, rots etc. can be identified. Further, in the case of several diseases, the spores, spore bodies, sporophores or such other structures produced by the pathogens can also be seen and the diseases can be identified. So, a basic knowledge about the disease symptoms, the causal organisms responsible for causing the diseases, their life cycle, reproductive capacity, mode of survival and spread of the pathogens etc. goes a long way in adopting appropriate control measures to combat the diseases. Diseases may spread through air, water, soil, seed or vegetative propagating materials. Many virus and mycoplsma diseases are spread through insect and non-insect vectors actively or passively. Control measures and plant protection chemicals to be used for the control of different diseases differ depending upon the causal organisms and other characteristics of the pathogens.
Various measures under evasion, exclusion, eradication and protection help to keep in check many plant diseases to a large extent. However, under certain circumstances, especially when the disease intensity crosses the economic threshold level, direct control measures by the use of plant protection chemicals have to be resorted to so as to control the disease and avoid economic losses. In this respect, knowledge about plant protection chemicals is also of vital importance.
To attain self-sufficiency in food production, plant protection is an essential and powerful tool. To use this tool effectively, it is quite important that we should acquaint ourselves with the various aspects concerning pathogenic microorganisms. This knowledge will serve as a basis for adopting suitable control measures at the appropriate time, thereby pave the way to maximize production.
In this context, we hope that this book, which has been brought out as per the syllabus of B.Sc.(Ag.) Degree course of the Agricultural Universities will be of immense help and guidance to the students of Agriculture, people working in the Department of Agriculture, people involved in Scientific Agriculture and the General Public.
Numerous illustrations have been given to enable the reader to understand the text easily and to make the study more interesting’
The authors are highly thankful to Dr.G.Kuppuswamy, Dean, Faculty of Agriculture, Annamalai University, Chidambaram, Tamil Nadu for having given the foreword to the book.
Acknowledgements are also due to friends and colleagues who have inspired, helped and encouraged the authors in their endeavor to complete the book successfully. The authors wish to express their sincere thanks to M/S. New India Publishing Agency, 101, Vikas Surya Plaza, Pitam Pura, New Delhi - 110 088 for the excellent manner in which this book has been brought out.
Preface
The ultimate aim of crop husbandry is to cultivate crops and obtain maximum returns according to their genetic potential. Pathogenic microorganisms stand in the way of crops attaining their full growth and maturity. Some plant pathogens, as a result of infection of the host plant may cause death of a part or the entire plant and cause total loss, while some others affect some parts of the plant resulting in reduction of yield. Some pathogens may affect the stored produce and cause spoilage. So, it becomes imminent that plant pathogens have to be controlled by adopting appropriate control measures so as to minimize the losses and maximize the yield.
The causative agents of diseases in plants include pathogenic microorganisms, such as fungi, bacteria, viruses, mycoplasma, protozoa and nematodes; phanerogamic parasites, algae and lichens of the Plant Kingdom; abiotic agents or unfavorable environmental factors, such as deficiency due to lack of certain macro or micro nutrients or toxicity due to excess of certain macro and micro nutrients; moisture, light or heat stress, as well as the presence of some toxic chemicals in the air, soil or water.
Plant pathology deals with the study of plant diseases caused by various pathogenic agents and environmental factors; the mechanisms by which these agents or factors induce diseases in plants; occurrence and mode of spread of the diseases and the methods of preventing or controlling them, thereby reduce the damage and consequent loss caused by them. As a separate field of Biological Science, Plant Pathology helps to enhance our knowledge about plant diseases, at the same time it tends to develop methods, equipments and materials through which plant diseases can be avoided or controlled.
In an ecological community, the majority of living organisms are plants. Plants have the ability to convert solar energy into chemical energy through the process of photosynthesis and this chemical energy is stored in the form of carbohydrates, proteins and fats in the plant cells. All vertebrates including humans, animals etc. and invertebrates, such as insects, nematodes etc. depend entirely on these plant materials for their survival and existence.
It has been established that microorganisms were present on this earth several thousands of years before humans and plants came into existence and had intruded into the world of microorganisms. These microorganisms, which had been living entirely on the organic matter for their sustenance, had gradually changed their mode of life and had become parasites on plants. These parasites, which cause various types of plant diseases, are known as plant pathogens.
Infection by plant pathogens invariably exhibits certain specific abnormalities in the host plants called disease symptoms. Each and every pathogenic microorganism produces quite different and distinct symptoms. These symptoms may be visible to the naked eye or in some cases may not be visible externally. From such characteristic symptoms, most of the diseases, such as leaf spots, blights, rusts, smuts, wilts, rots etc. can be identified. Further, in the case of several diseases, the spores, spore bodies, sporophores or such other structures produced by the pathogens can also be seen and the diseases can be identified. So, a basic knowledge about the disease symptoms, the causal organisms responsible for causing the diseases, their life cycle, reproductive capacity, mode of survival and spread of the pathogens etc. goes a long way in adopting appropriate control measures to combat the diseases. Diseases may spread through air, water, soil, seed or vegetative propagating materials. Many virus and mycoplsma diseases are spread through insect and non-insect vectors actively or passively. Control measures and plant protection chemicals to be used for the control of different diseases differ depending upon the causal organisms and other characteristics of the pathogens.
Various measures under evasion, exclusion, eradication and protection help to keep in check many plant diseases to a large extent. However, under certain circumstances, especially when the disease intensity crosses the economic threshold level, direct control measures by the use of plant protection chemicals have to be resorted to so as to control the disease and avoid economic losses. In this respect, knowledge about plant protection chemicals is also of vital importance.
To attain self-sufficiency in food production, plant protection is an essential and powerful tool. To use this tool effectively, it is quite important that we should acquaint ourselves with the various aspects concerning pathogenic microorganisms. This knowledge will serve as a basis for adopting suitable control measures at the appropriate time, thereby pave the way to maximize production.
In this context, we hope that this book, which has been brought out as per the syllabus of B.Sc.(Ag.) Degree course of the Agricultural Universities will be of immense help and guidance to the students of Agriculture, people working in the Department of Agriculture, people involved in Scientific Agriculture and the General Public.
Numerous illustrations have been given to enable the reader to understand the text easily and to make the study more interesting’
The authors are highly thankful to Dr.G.Kuppuswamy, Dean, Faculty of Agriculture, Annamalai University, Chidambaram, Tamil Nadu for having given the foreword to the book.
Acknowledgements are also due to friends and colleagues who have inspired, helped and encouraged the authors in their endeavor to complete the book successfully. The authors wish to express their sincere thanks to M/S. New India Publishing Agency, 101, Vikas Surya Plaza, Pitam Pura, New Delhi - 110 088 for the excellent manner in which this book has been brought out.
