Report on Plant Diseases. 
By Ernst A. Bessey. 
Mr. President, Ladies and Gentlemen: 
Owing to lack of the necessary time 
in which to prepare a more extended pa¬ 
per I shall confine my remarks to two 
topics, viz.: withertip fungus and nema¬ 
todes. 
In taking up the first-named topic I 
realize that I am entering upon a field 
well worked by our respected President, 
but I am sure he will pardon me if I ap¬ 
pear to trespass upon his preserves. 
As Professor Rolfs demonstrated some 
years ago and made known in addresses 
before this society, as well as in Govern¬ 
ment publications, various citrus diseases 
including withertip, blossom blight and 
tear-staining of pomelo, lemon spot, and 
several other troubles are caused by the 
fungus Colletotrichum gloeosporioides. 
Of course, not all cases of dying back of 
twigs, nor of the rotting of fruits are 
due to this cause, for other organisms as 
well are capable of causing these injuries, 
but in a large proportion of cases the 
fungus above named is responsible. 
Under Professor Rolf’s direction, be¬ 
fore he severed his connection with the 
Subtropical Laboratory, inoculation ex¬ 
periments were begun, which have been 
continued with some interruptions under 
my direction since I assumed charge of 
the Laboratory. These have demonstrated 
that this fungus is the same one that 
causes the blossom-blight, leaf-spot and 
fruit-rot of the mango and avocado, the 
tear-staining of the mango and leaf-spots 
and fruit-rots of various other plants. 
These investigations make it almost cer¬ 
tain, furthermore, that this fungus is, if 
not identical with, at least but a slight 
modification of the fungus that causes the 
bitter rot of apples. We see, therefore, 
that it is not a fungus confined to but 
one or two hosts in a limited area with 
which we have to contend, but one of 
wide distribution, and capable of attack¬ 
ing a great many kinds of plants. I have 
found apparently the same fungus on over 
fifty plants at Miami, some of them com¬ 
mon weeds. This explains why, when 
the weather conditions or other circum¬ 
stances are favorable, the disease springs 
up everywhere all at once, without any 
very apparent center of infection. Fur¬ 
ther complicating the matter is the fact 
that the fungus is not confined to living 
plants, but will grow with great readi¬ 
ness—I will not say equally well—on 
dead parts of the same or other plants. 
Often we find that citrus trees dying 
back from some other cause, e. g. die- 
back or blight, show this fungus in abun¬ 
dance on the dead branches, although in 
this case the fungus has appeared after 
the death or weakening of the tissues by 
the other disease. 
In view of the above mentioned facts, 
we see why it is so desirable to keep the 
grove clean, trimming off and burning 
all dead branches, and destroying all 
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