67 
ROOT-ROT OF LEMON. 
(Phoma omnivorciy n, sp.) 
It is only quite recently that I have had an opportunity of 
examining this disease, as it has probably hitherto been confounded 
with u Collar-rot.” The first mention of it, as far as known to me, 
is by Mr. W. S. Williams, of Doncaster, who referred to it at the 
Conference of Australasian Fruit-growers, held at Brisbane, in 
1897, in the following terras:-—“ This disease is of a more deadly 
character than Collar-rot, as it begins in the subsoil at the 
extremities of the roots, and proceeds upwards until the tree dies. 
Once a tree is affected there is no cure. The cause of this disease 
is bad drainage and stagnant water, which poisons the roots ; or 
it may also be caused by some deleterious substance in the subsoil, 
such as salt, copper, antimony, or other poisonous minerals. 
Many people mistake it for collar-rot, but they are totally different 
in their symptoms, and brought on by totally different causes.” 
Symptoms and effects .—The trunk and main roots of a Lemon 
tree suffering from this disease were kindly forwarded to me by 
Mr. Williams for examination. The half-dead roots were seen to 
have lost the outer bark for a considerable distance, and the inner 
layer showed numerous pustules of Phoma omnivora . The colour 
of the diseased part was dark-brown, in parts almost black. On 
examining portions of the outer bark on the other side of the 
same roots, the fungus was also met with. On other roots, 
seemingly quite sound, there were small black patches seen to be 
due to the numerous pustules of the fungus, though at almost any 
part of the roots the fungus could be found on microscopical 
examination, not being visible to the naked eye. The earth and 
soil adhering to the roots in many cases hindered the discovery 
of the fungus, and of course its presence would not bo suspected 
by the ordinary observer. 
It was remarkable that the Phoma could he fouud on the roots 
at a depth of not less than 10 inches below the surface of the 
soil and extending all the way up the trunk, at least to the 
limit of the specimen sent, which was cut off fully 6 inches above 
the ground. Thus, allowing for the bend in the roots at junction 
with the trunk, a length of over 2 feet was attacked with greater 
or less severity by the fungus, and no roots were found entirely 
free from it. 
On the side of the stem to which the decayed roots belonged, 
the bark rotted away as in the case of Collar-rot (but without the 
accompanying gumming), and this could easily be accounted for 
from the necessary nourishment not being supplied on that side. 
Mr. Williams had noticed this particular tree failing for a year or 
more, and he believes that the points of the roots went first. 
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