Host Plants and Their Diseases - Westcott's Plant Disease - page 420

section, Part IV , the key word, for example rot or blight, is given in “cap and

small caps” (an initial capital followed by small capitals), followed by the name
of the pathogen in boldface. In the disease section (

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Part III ) the pathogens
are likewise listed in boldface, but in alphabetical order under each heading such
as rot or blight, and then the common name of the disease is given in cap and
small caps.
For instance, your acacia seems to be dying, and you think it may have
a root rot; perhaps you can see objects like toadstools at the base. You look up
ACACIA and check the possibilities until you come to the line: ROT,
Mushroom Root. Armillaria mellea, occasional; Clitocybe tabescens, FL.
“Occasional” means that this rot might be found wherever acacias grow.
You live in California so you turn to the section head

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Part III
and thumb down through the A's until you come to ARMILLARIA. Under
the name is the classification of the genus, but you can leave that to the
pathologist and go to: “Armillaria mellea; MUSHROOM ROOT ROT of
trees and shrubs, also known as Armillaria root rot or toadstool disease.” You
learn that this disease is especially common in California, and that the honey-
colored mushrooms or toadstools are not always present for diagnosis but that
black shoestrings are also telltale characters. You conclude that this is your
fungus, and you read on to see what can be done to the soil to prevent
a recurrence of the problem. But before you do anything too drastic, you should
discuss the whole situation with someone at the University of California, for
you could be mistaken.
It cannot be expected that a gardener can make accurate diagnosis of
disease from reading this Handbook any more than reading a medical topic
can turn a layperson into a doctor. It takes years of experience to recognize
diseases on sight, from macroscopic symptoms, and it takes some technical
training to recognize diseases by studying the fungus under the microscope
and perhaps growing it in culture. For airtight identification of a bacterium or
fungus with a new disease the organism must be repeatedly isolated in
culture; the disease must be produced in healthy plants by inoculating them
with a pure culture of the organism; and then the fungus, or bacterium, must
be reisolated from the artificially infected plant.
In some cases the small number of known diseases for a plant together with
their distinctive type and geographical distribution makes layperson identifica-
tion relatively reliable. In other cases, specific identification, other than to know
that it is a leaf spot, is unnecessary. And in still other cases, specimens should be
sent to your state experiment station for diagnosis. It is my hope that the
overburdened extension pathologist, receiving some unusual specimen, will
find this list of host plants and their diseases of value in speeding up
identifications.

ROTS in

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