XIV, G 
Lee and Yates: Pink Disease of Citrus 
663 
DISSEMINATION OF THE FUNGUS 
Very little is known about the means of dissemination of the 
fungus. Our observations upon the pustule, or “Hbckerchen,” 
stage have always shown it to be sterile. We have always ob- 
served the pink incrustation, which is the most noticeable stage 
of the fungus, to be sterile upon Citrus. Brooks and Sharpies 
report and figure basidiospores upon the pink incrustation 
formed on rubber, but we have not observed them on the in- 
crustation as it occurs upon Citrus. 
Plate II, figs. 3 and 4, show the gross appearance of the stage 
first described by Massee as Necator decretus. This stage is 
found very abundantly on Citrus during the early months of 
the rainy season, usually upon wood that has been previously 
killed by the fungus. It is conspicuous for its bright oi*ange 
color (bitter-sweet orange of Ridgway), very distinct from the 
pink color of the sterile mycelium of the fungus. Irregularly 
shaped, thin-walled spores are formed abundantly in this stage; 
and these spores would appear to be the principle means of 
dissemination of the fungus, at least over any considerable 
distance. This fact assumes a bearing on the methods of control, 
since it indicates the value of the removal of all twigs and 
branches affected with the disease before the appearance of the 
Necator stage. The Necator stage as it occurs on rubber has 
been well figured and described by Brooks and Sharpies; and, 
in general, our observations of this stage on Citrus, confirm 
their conclusions. 
CONTROL EXPERIMENTS 
In the fall of 1917, in connection with experiments in the 
control of citrus canker conducted at Lamao experiment station 
by the senior author, control methods against Corticium were 
also taken up. The orchards (Selected at Lamao for the citrus- 
canker experiments were so badly affected with pink disease 
that control measures were desirable in order that they might 
be maintained in good condition. 
In the past, control measures against pink disease have been 
for the most part based upon the removal of affected tree parts, 
followed by disinfection. A number of disinfection . methods 
have been practiced, probably the most commonly employed 
being the application of tar. Van Hall suggests carbolineum 
“ Van Hall, C. J. J., Cocoa. Macmillan & Co. Ltd., London (1914) 252. 
