CHAPTER ONE
1.0 INTRODUCTION
A large number of chemicals have been developed for the control of plant diseases,
but due to the growing awareness of the hazardous side effects of these chemicals, more
emphasis is given to the use of biocontrol agents. One of the major challenges in the field
of Plant Pathology is the need for some ecofriendly and safe alternative control strategies
for agriculture, which has led researchers to turn their attention to plant extracts as sources
of biocontrol agents. Therefore, growing of most plants and tress now goes beyond
afforestation purposes to making them available and accessible for exploitation for their
natural chemical composition vis-Ã -vis their usefulness in the management and cure of
both plant and animal diseases. These chemical compounds, known also as
phytochemicals, provide defenses for the plants against diseases and other environmental
factors. It is now evident that most of these plant chemicals could also be helpful in the
treatment of both animal and human diseases. These phytochemicals which are bioactive
include alkaloids, flavonoids, steroids, saponin, tannins, terpenoids, glycosides and other
phenolic compounds classified as most important (Edeoga et al., 2006). Most of these
phytochemicals are used in the control of animal and plant diseases for their rich
composition, which provides both preventive and curative properties.
The use chemicals has helped increase yield obtained but one of the major problems
of the constant use of chemicals is the development of resistance in the target organisms.
Studies in the use of plant extracts for the control of plant diseases have shown the
importance of natural chemicals as a natural source of non-phytotoxic and easily
biodegradable alternative fungicides and antibiotics (Akueshi et al., 2002).
Fungal diseases of plants destroy 10-30% of the total yield of crops and in some
perishable fruits and tubers especially in developing countries; they destroy more than
30% of the crop yield (Kader, 2002). The quality of Irish potato is adversely affected by
post-harvest handling, packaging and transportation which result in decay by
microorganisms which become activated because of the changing physiological state of
the produce (Agrios, 2005). Among the prevalent diseases recorded and the increased use
of plants in areas of disease control has raised concerns about the side effects of
agrochemicals (Kader, 2002).
1.1 JUSTIFICATION FOR THE STUDY
Fungi are the most prevalent pathogens affecting a wide range of host plants. This is
often facilitated by colonization of wounded and exposed plant tissues which in turn bring
about destruction and losses of economically important food crops. The ease of spoilage
(especially after harvest) of plant produce could be attributed to improper storage,
transportation, handling and marketing as acknowledged by the international monitoring
world food resources unit (Weber, 2003). In view of these losses, man has resorted to the
use of agrochemicals (biocides) in his agricultural practices desp
1.0 INTRODUCTION
A large number of chemicals have been developed for the control of plant diseases,
but due to the growing awareness of the hazardous side effects of these chemicals, more
emphasis is given to the use of biocontrol agents. One of the major challenges in the field
of Plant Pathology is the need for some ecofriendly and safe alternative control strategies
for agriculture, which has led researchers to turn their attention to plant extracts as sources
of biocontrol agents. Therefore, growing of most plants and tress now goes beyond
afforestation purposes to making them available and accessible for exploitation for their
natural chemical composition vis-Ã -vis their usefulness in the management and cure of
both plant and animal diseases. These chemical compounds, known also as
phytochemicals, provide defenses for the plants against diseases and other environmental
factors. It is now evident that most of these plant chemicals could also be helpful in the
treatment of both animal and human diseases. These phytochemicals which are bioactive
include alkaloids, flavonoids, steroids, saponin, tannins, terpenoids, glycosides and other
phenolic compounds classified as most important (Edeoga et al., 2006). Most of these
phytochemicals are used in the control of animal and plant diseases for their rich
composition, which provides both preventive and curative properties.
The use chemicals has helped increase yield obtained but one of the major problems
of the constant use of chemicals is the development of resistance in the target organisms.
Studies in the use of plant extracts for the control of plant diseases have shown the
importance of natural chemicals as a natural source of non-phytotoxic and easily
biodegradable alternative fungicides and antibiotics (Akueshi et al., 2002).
Fungal diseases of plants destroy 10-30% of the total yield of crops and in some
perishable fruits and tubers especially in developing countries; they destroy more than
30% of the crop yield (Kader, 2002). The quality of Irish potato is adversely affected by
post-harvest handling, packaging and transportation which result in decay by
microorganisms which become activated because of the changing physiological state of
the produce (Agrios, 2005). Among the prevalent diseases recorded and the increased use
of plants in areas of disease control has raised concerns about the side effects of
agrochemicals (Kader, 2002).
1.1 JUSTIFICATION FOR THE STUDY
Fungi are the most prevalent pathogens affecting a wide range of host plants. This is
often facilitated by colonization of wounded and exposed plant tissues which in turn bring
about destruction and losses of economically important food crops. The ease of spoilage
(especially after harvest) of plant produce could be attributed to improper storage,
transportation, handling and marketing as acknowledged by the international monitoring
world food resources unit (Weber, 2003). In view of these losses, man has resorted to the
use of agrochemicals (biocides) in his agricultural practices desp
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