Apr. ax, 1933 
Gummosis of Citrus 
221 
cuts not inoculated, made as controls, healed without visible injury to 
the tree. 
As indicated by these inoculations, the attack of Sclerotinia lihertiana 
may be very severe and its progress very rapid for a comparatively short 
time, and then it may be quickly halted. If the tree trunk attacked is 
small, girdling and death may result, while on a large trunk with not 
more than one point of infection, self-recovery may take place. Observa¬ 
tion shows that the halting of the invasion is usually coincident with the 
formation and exudation of considerable quantities of gum. 
EXPERIMENTS TO TEST THE POSSIBLE RELATION OP OTHER ORGANISMS 
TO GUMMOSIS 
A number of other organisms, most of which were found commonly 
on dead or decaying bark of Citrus trees, were used in inoculation experi¬ 
ments to ascertain their relation, if any, to gummosis. 
The results of inoculations with various cultures of Fusarium sp., 
commonly found associated with Pythiacystis gummosis, have already 
been presented on page 205. The effect of Fusarium alone was insig¬ 
nificant. The death of the bark at the inoculated cuts was inconspicuous, 
and only slight death of the outermost layer of bark resulted over small 
areas. Only part of the inoculations produced gum, usually in small 
quantity. 
Penicillium roseum was frequently found on dead bark affected with 
gummosis. The results of some of the inoculations with pure culttures of 
this fungus are presented in Table XV. 
Table XV .—Inoculations with Penicillium roseum at Santa Paula 
Bxperi* 
xnent 
No. 
Date of inoculation. 
Kind of inoculation. 
Gum. 
Initially 
kill^ bark 
at inocula¬ 
tion point.* 
Cracking of 
outer bark.* 
I 
July 12,1912 
Vertical slit 2 cm. long, covered 
with oiled paper. 
2 
I 
2 
2 
Aug. 23,1912 
Vertical slit. 
2 
1 
0 
3 
Feb. 21,1913 
Vertical slit not protected. 
2 
I 
2 
4 
.do. 
Controls on same trees as above... 
0 
0 
0 
5 
Feb. 20,1913 
Vertical slit not protected. 
I 
I 
0 
6 
.do. 
Control on same tree.. 
0 
I 
2 
x**sli 2 ht, d»-iiiedium. 
Gumming was induced in all the cuts inoculated with Penicillium 
roseum in Table XV. The dead bark adjacent to the inoculated cuts 
was slight in amount. The outer layer of bark surrounding two of the 
inoculated cuts and only one of the controls died and cracked. 
Inoculations were made with a number of other organisms, as shown 
in Table XVI. All of these were found on Citrus trees except Coryneum 
berynkii and Pseudomonas cerasius. 
