57 
“COLLAR ROT” OR “MAL DI GOMMA” 
(Fnsarium limonis, Briosi.) 
This disease being so widespread, has naturally a variety of 
names, and it is necessary to know the principal ones in order to 
understand the references made to it in various publications. It 
is commonly called “Collar rot,” because it attacks the lower 
portion of the stem near the ground, and may either be below or 
above it. “Foot rot” has a similar signification, and the com¬ 
mon Italian name of “Mai di gomma,” or gum disease, indicates 
that gumming is a constant accompaniment of the disease. It 
is sometimes referred to as the fatal “ Bark disease,” but as 
several different diseases may be included under this term, it 
ought to be discarded. It is also known as “ Sore shin ” and 
“ Bark rot,” from the part affected, “ The Fatal ” from its 
destructive character, and the “ Sydney disease ” from being so 
common about Sydney; but the common name with us is 
“ Collar rot.” It is, unfortunately, one of the best known of 
Citrus diseases, for it occurs wherever Oranges and Lemons 
are grown, often causing serious loss. The first mention of it 
was in connexion with the Orange groves of the Azores, where it 
seems to have originated, and was noticed as early as 1832. Like 
many other diseases, it attained its maximum, then began to 
decline, and about. 40 years afterwards its force was spent, and 
it ceased to be regarded as serious. 
Meanwhile, it spread to Southern Europe, and afterwards 
appeared in Florida and California. It has now obtained a foot¬ 
ing in Australia, and annually causes considerable loss. From 
the very nature of the disease, which attacks young and old trees 
alike, and may sometimes “ring-bark” them in the course of a few 
months, entire groves are either destroyed or rendered almost 
worthless. It is generally spoken of as a mysterious disease, but 
the discovery of the parasitic fungus causing it has brought it 
within tho domain of rational treatment. 
Symptoms .—The disease has often made considerable progress 
before the grower is aware of its presence, because it begins so 
low down that it is overlooked. One of the first indications is 
the exudation of drops of gum at the neck of the tree, and this 
is so constant that whore there is no gumming some other disease 
is at work. It would appear that the fungus parasite excites the 
How of gum for its own convenience, for I found numerous conidia 
actively germinating in it and producing filaments at either end 
or laterally. The gumming may occur at one or more spots, and 
the bark at the same time becomes discoloured. The browning 
of the bark is the sign of rotting which gives rise to a decidedly 
disagreeable odour, and the bark gradually rots away and is 
thrown off. If the tree is able to renew the bark and arrest the 
