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Return to
Lead Story

Biodiversity and
Plant Pathogens
and Conservation

by Dr. David Ingram

Participate in an
Discussion on
Plant Pathogen Conservation

British Mycological
Society Draft Policy
On Conservation
of Fungi

Six Reasons to
Value the Biodiversity
of the Earth

Vole Power:
Herbivores Prefer
Diseased Plants

A Study of Two
Oak Species and
Powdery Mildew

What is
Plant Pathology?

   Related Reading:
Potato Late Blight and
   the Irish Potato Famine
   Why Europeans
   Drink Tea

   Meltdown for

Link to the site of the
7th International
Congress of Plant

The American
Phytopathological Society
3340 Pilot Knob Road
St. Paul, MN
55121-2097 USA
e-mail: aps@scisoc.org

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What is Plant Pathology?
Why is it Important?
by Avice Hall, University of Hertfordshire, UK

Plant Pathology is the study of the diseases and disorders of plants. Disease can be defined as a harmful deviation from normal functioning of the physiological processes caused by an infectious agent. In the case of plant diseases, the causal agent maybe a fungus, virus, bacterium or a parasitic flowering plant. (A 'harmful deviation' caused by a non-infectious agent, for example, herbicide or nutrient deficiency, is a disorder.)

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Top, an example of a rust fungus on a bean leaf. At right, an example of a parasitic flowering plant, bloomrape.

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Much of the time plant pathologists study diseases of crop plants. These diseases have had a huge impact on crops and subsequently on human history. One hundred and fifty years ago the potato crops of much of Europe including Ireland were devastated by the potato blight fungus, Phytophthora infestans, an introduced pathogen on a non-native crop. The ravages of this disease lead to 1 million deaths and 1,500,000 emigrations from Ireland alone. One hundred years ago the coffee rust fungus, Hemileia vastatrix, caused such devastation in the coffee plantations of what is now Sri Lanka that all coffee was dug up and replaced with tea. Fifty years ago an epidemic of brown spot on rice, caused by Cochliobolus miyabeanus, in what is now Bangladesh led to many thousands of deaths from starvation. On the 5th of  May this year, a headline in the British newspaper proclaimed 'Meltdown for Chocoholics'. Further reading revealed that the culprits for this crisis were two diseases of cocoa, witches broom and black pod.

Most plant pathologist spend their time studying several of the thousands of diseases of crop plants and working to limit the damage caused by these infectious agents.  Eradication may be aimed at removing completely the causal agent of a particular disease, or under some circumstances, the eradication program may be aimed at the alternate host of the pathogen (the infectious agent frequently survives the intercrop period on a totally unrelated host, the alternate host). Eradication of this host  removes an essential part of the pathogen's lifestyle. Examples of this include the removal of Ribes spp. to control White Pine Blister rust, or barberry to control black stem rust of wheat. Grubbing up a diseased plant and burning it is a very effective control method.

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Puccinia graminis on barberry

If this is the case do 'Conservation' and 'Biodiversity' have anything to do with Plant Pathology? Or are Plant Pathologists the only professionals on earth paid to eradicate rare and endangered species and not to be involved in conservation or Biodiversity Action? While there are some conservation initiatives for fungi (mainly aimed at macro fungi and not plant pathogens) there is virtually nothing that involves the conservation of  fungal plant pathogens, bacteria or viruses. The World Health Organization rejoiced when smallpox was eradicated as a disease, but some samples of the causal agent have been 'conserved' for future reference.

What should the attitude of Plant Pathologists be towards conservation and biodiversity initiatives? Read on and interact with this site.

Copyright 1998 by The American Phytopathological Society
Copyright 1998 by The British Society for Plant Pathology