10 BULLETIN 684, U. S. DEPARTMENT OF AGRICULTURE. 
LIFE HISTORY. 
In the literature pertaining to bitter-rot cankers there is very 
little to be found on the subject of their development and length 
- of life. Spaulding and Von Schrenk (13) state— 
The majority of the cankers found during the last summer probably were 
started two years ago. During the first year the fungus made very little head- 
way. A very small central area was killed, generally around and including a 
small branch. The following year the large part of the canker was formed. 
Whether the cankers will continue to increase in size is as yet undetermined, 
but it does not seem probable, for if such were the case cankers 3 or more years 
old ought to have been secured in the orchards where the bitter-rot has been 
common for many years. 
On many varieties the writer has not been able to find any very 
old cankers, but in the case of very susceptible varieties, such as 
Givens, he has found many cankers which have attained apparent 
ages of 8,10, and more years. One limb, which by count of annual 
rings was 13 years old, bore a canker which showed 11 zones, in- 
dicating that the canker had passed through 11 growing seasons. 
Cankers were found growing on main limbs which were evidently 
much older than this. In order to trace the development of cankers, 
the writer in 1914 made some preliminary inoculations of apple 
branches with spores from pure cultures of Glomerella cingulata. 
Inoculations were made by introducing newly formed conidia into 
small slits artificially made in the bark. The slits were at once cov- 
ered with absorbent cotton moistened with distilled water, which was 
allowed to remain for one week. Controls consisted of branches 
similarly treated except that no conidia were placed in the slits. 
In Arkansas on September 14, 1914, thé following inoculations and 
control experiments were made, using as inoculum conidia from 
corn-meal cultures of the fungus isolated from a canker on August 3: 
Three inoculations in slits in 2-year-old branches. 
One control slit in a 2-year-old branch. 
One inoculation in a slit in a 1-year-old branch. 
One control slit in a 1-year-old branch. 
The tree used was a 15-year-old specimen of the Missouri variety. 
The weather had been hot and moist and accordingly was quite 
favorable for the development of the fungus. 
When the absorbent cotton was removed one week later it was 
evident that the inoculations had been successful. About the slits 
into which the conidia had been introduced the bark was blackened 
and sunken in a ring from 1 to 2 mm. in width, whereas only the cut 
surfaces of control slits were blackened. By October 7 the inocu- 
lated slits formed the central portions of rapidly growing cankers. 
At that time the fungus on the 2-year-old branches had developed 
until the blackened, sunken areas had attained lengths varying from 
