104 
THE NATIONAL NURSERYMAN 
Attractive Looking Office of the Elizabeth Nursery Co., Elizabeth, New Jersey 
A STUDY OF THE CONTROL OF CROWN GALL ON 
APPLE GRAFTS IN THE NURSERY 
By I. W. Me thus and T. J. Maney 
Research Rulletin No. 69 sent out by the Agricultural 
Experiment Station, Ames, Iowa, gives the following 
summary of its investigations in relation to the control 
of crown gall on apple grafts in the nursery: 
Conclusions 
The following tentative conclusions seem justifiable 
from the experiments recorded. 
The infection of apple grafts is readily accomplished 
hy dipping the grafts just before planting in a viable 
bouillon culture of Bacterium tumefalciens. The ma¬ 
jority of the galls occur at the union. The stock is less 
liable to become infected than the scion. 
Apple grafts were apparently equally susceptible to 
the crown gall organism where the callous was normal, 
excessive or slight. 
Well made and poorly made grafts showed little dif¬ 
ference in the amount of crown gall that developed. 
Using an unusually large amount of string over the 
union of the grafts leads to girdling and excessive cal¬ 
lousing of the trees, which seems to facilitate crown gall 
infection. Cloth applied over the union as a wrapper, 
either with or without string, decreases the amount of 
crown gall. 
Scion wood cut from trees infected with crown gall at 
the union did not show any increased amount of crown 
gall. 
Hairy root seedlings, when used as stock, did not 
transmit hairy root to the scion, but the stock portion of 
the graft remained infected in the majority of cases. 
Most of the crown gall infection takes place the first 
year on the grafts, during the formation of the callous, 
at the union. 
Surface disinfection with formaldehyde (.16 percent) 
copper sulfate (.26 percent) and mercuric chloride (.1 
percent), were seriously injurious to callousing of ap¬ 
ple grafts. Fungicides which go into solution slowly, 
such as lead arsenate and bordeaux mixture, have a 
much less injurious effect on the callousing process. 
A strong bordeaux mixture (26-26-60) decreases the 
stand, tends to have a preserving action on the string 
and reduces the amount of crown gall. 
Resin sticker added to bordeau mixture increases 
its toxic action and reduces the stand. The addition of 
lead arsenate or soaps to bordeaux mixture does not in¬ 
crease its toxic action on the grafts, but rather increases 
its adhesiveness and its fungicidal efficiency. 
More dilute bordeaux mixtures did not reduce the 
stand and proved nearly as beneficial in reducing crown 
gall as the stronger mixtures. The use of bordeaux 
mixture (8-8-60), with or without lead arsenate, re¬ 
duced the percentage of crown gall about 66 percent 
over the checks, and nearly 60 percent over the mean 
percent of crown gall in all the checks in the Wealthy 
variety. 
