Mar. i, 1924 
An Apple Stem Tumor Not Crowngall 
697 
Martin, Buckskin, Grimes, Ben Davis, Barnes’ Best, Ensee. There were 
10 varieties in an orchard examined which were less susceptible than 
the above named in varying degrees. All had woolly aphis rootgalls. 
The stem-tumors varied in size and number (PI. 2, B and C) and on 
some trees there were indications that the tumors had kept on develop¬ 
ing for some years; then some change in conditions took place and the 
newer branches were clean, since few or no tumors had formed during the 
last years. Four apple varieties in this orchard, Titavka, Loy, Bethlemite 
and Van Hoy, had no stem- or root-tumors and did not seem susceptible. 
The first three varieties had no woolly aphids on them anywhere. 
Although Van Hoy had some of the woolly aphids on the young twigs 
there were no swellings. 
In a young orchard consisting of 58 apple trees, two of which were the 
Early Harvest variety, these two were the only ones with the woolly 
apple aphis on the stems and the only ones with stem-tumors. 
Other varieties, such as the Chenango, Spitzenberg and King, affected 
with stem-tumors, were received from various parts of the United States. 
A bad feature of the numerous stem-tumors on apple trees is the 
opportunity it provides for secondary organisms to get into the stem 
and ultimately cause more damage than the stem-tumor itself. The 
tumors are composed partly of soft cortex tissue which wood-invading 
insects can feed on and get through into the deeper portions of the stem, 
continuing their work of invasion throughout the year and forming 
great holes. The movement of sap is, of course, interfered with, which 
in turn affects the whole life processes of the tree. The breaks in the 
surface of the bark where the tumors push through likewise offer an 
entrance for the pear-blight organism, Bacillus amylovorus, which also 
causes greater damage than the stem-tumor (PI. 2, D). 
From the report of the results of Dr. J. J. Taubenhaus’ work 3 with 
apple stem-tumor, it seems that Bacterium tumefaciens may occasionally 
cause stem-tumor on apple tree perhaps similar in appearance but of 
different origin from that described in this pa£>er. 
It is theoretically possible for Bacterium tumefaciens to produce tumors 
naturally on apple stems as well as on the crown and roots, for galls 
have been produced artificially by inoculating apple stems with Bacte¬ 
rium tumefaciens (Pi. 1, B). So far as .the writer’s observation goes, this 
organism confines its work in nature to the production of galls and hairy- 
roots on both crown and roots of apple trees. The cases of apple stem- 
tumor from various parts of the United States examined by the writer 
did not contain Bad. tumefaciens in a single instance. 
CONCLUSIONS 
Outgrowths on stems of apple trees herein described, and heretofore 
generally believed to be due to infection by Bacterium tumefaciens , the 
organism producing typical crowngall, are not secondary outgrowths 
from tumor strands nor are they primary infections of the crowngall 
organism. Although such conditions have not been observed by the 
writer, it is possible that in some regions there may be aerial tumors for 
which the crowngall organism is responsible. 
3 Adams, J. F. diseases op fruit and nut crops in the united states in 1922. U. S. Dept. Agr. 
Bur. Plant Indus. Plant Disease Bui., Sup. 28, p. 308. 1923. (Mimeographed.) 
