Agriculture Reference
In-Depth Information
1
PLANT DISEASES - AN
INTRODUCTION
Humankind has struggled with plant diseases since the
dawn of agriculture. There are references in the Old
Testament to the ravages of rust and blight on cereals
and grapevines in the ancient world. The potato famine in
Ireland in the 1840s led to the mass migration of Irish
refugees to Australia, Britain and North America so
that today, almost one in 10 Australians can trace their
ancestry back to Ireland. The cause of the famine was
the potato blight pathogen
Phytophthora infestans
, which
destroyed plants and tubers under prolonged wet and
cold weather.
Plant diseases are intimately connected with current issues
facing agriculture and the environment. Global warming
and rainfall reliability will have a considerable inf luence on
Fig 1.1 Healthy produce is a team effort between growers, horticulturists and plant pathologists.
disease distribution and severity in crops. Plant diseases are
a major factor in world food security and biosecurity issues
are a key component in international trade agreements. The
absence of many damaging pathogens in Australia provides
competitive advantage in trade and access to new markets.
Furthermore, savings in costs associated with managing
or eradicating these pathogens means that, in some cases,
production is more efficient and sustainable than in
overseas countries.
Causes of disease in plants
A simple definition of a plant disease is any disturbance
that interferes with the plant's normal structure, function
or economic value. Plant diseases divide conveniently into
(a) those caused by parasitic microorganisms or
pathogens, and (b) non-parasitic diseases or disorders.
These latter include mineral excesses and imbalances,
incorrect storage conditions after harvest, environmental
inf luences (such as atmospheric pollutants) and herbicide
damage. Table 1.1 lists some physiological disorders of
perennial fruit crops.
Fig 1.2 The healthy farm (above) used the latest disease management
systems. The sick farm (below) allowed the root rot disease
Phytophthora to develop.
