Nov. 15, 1925 
Crown-gall Studies of Resistant Stocks for Prunus 
969 
readily be performed without any great technical skill. A limited 
amount of experimental work in inarching Prunus into diseased apri¬ 
cot trees on peach stock has given very satisfactory results. 
Table VIII .—Results after two years’ growth in soil inoculated with minced galls 
at the time of planting 1-year-old trees, 6 to 8 inches high 
Stock 
Common name 
Source • 
Number 
of trees 
Number 
with galls 
P. cerasifera.. 
Myrobalan__ . __ 
NS_ 
139 
4 
P. cerasifera (hybrid)_ 
Marianna_ _ ... 
NS_ 
155 
7 
P. insititia. _ 
St. Julian plum_ _ 
NS_ 
48 
2 
A. davidiana- _ 
Davidiana peach _ _ ___ 
USDA_ 
41 
35 
P. americana . 
American plum__ 
AA_ 
56 
2 
P. munsoniana 
Wildgoose plum _ ____ 
AA.. 
18 
0 
P. besseyi 
Sand cherry_ 
NS_ 
49 
2 
P. mume_ 
Japanese apricot__ _ 
USDA_ 
16 
0 
P. domestica. 
P. D. stock b _ _ __ 
NT_ 
27 
0 
P. americana . 
Sprouts from old tree c __ 
17 
0 
°The explanations of the letters used in Tables I, II, and VIII may be found under “Sources of mate* 
rial.” 
b Prunus domestica, a rootstock secured from sucker in a commercial orchard, and used to a limited 
extent in California. 
«The sprouts of P. americana were secured from a tree (now dead) in the Botanical Garden, University 
of California. 
GERMICIDES IN THE NURSERY 
In the tests reported in Table VII certain of the germinating pits 
of apricot and peach were covered with a Bordeaux paste before 
planting. When this had become dried the pits were planted with 
and without minced galls. After two years no difference could be 
found between these trees and those growing in adjacent rows not 
treated with Bordeaux paste but inoculated with gall fragments. 
Table IX is a summary of tests made by using different germicides 
on peach roots to protect them from infection with the gall organism 
when inoculated with fragments of peach galls. The peach roots 
were two years old, and none of them showed any evidence of crown 
gall when planted. 
Slight injuries were made on the roots by light scraping before 
treatment with germicide. The gall fragments were mixed with the 
soil at the time of planting. The results indicate that under the 
conditions of the experiment the germicides were not very effective 
in preventing the development of crown gall, although in all tests 
but one there was a reduction in the percentage of galled trees. 
The conditions in all cases were much more favorable for infection 
than under usual orchard practice, in that there was abundant 
inoculum and injuries favorable for infection. All the germicides 
were more or less injurious to the roots, as was indicated by the 
number of trees dying as compared with the controls. The Bordeaux 
paste was no more efficient than the 12-15-50 Bordeaux mixture. 
These results are much less promising than those of Melhus and 
Manley (I), who, by using Bordeaux paste on bench-grafted apple 
roots, obtained very good results. The large amount of inoculum 
present in these tests of the writer may possibly explain the differ¬ 
ence in results, and apples are possibly less susceptible than peaches 
