CROWN GALL. 
By Wendell Paddock. 
The subject of crown gall is one of vital importance in Colo¬ 
rado, since under our conditions the organism that is responsible 
for this disease of fruit trees and plants, finds congenial surround¬ 
ings for growth and distribution. 
The so-called galls are irregular outgrowths of tissue that 
commonly form around the crown of a tree just below the surface 
of the ground. They also occur frequently on the roots, but are 
quite different in appearance from the swellings that are produced 
by the attacks of woolly aphis, which unfortunately are also very 
destructive in our State. 
The galls increase rapidly in size, when the conditions are 
favorable, and so interfere with the process of nutrition that the 
vigor of the tree is greatly impaired. In many instances the 
death of the tree is but a matter of a few years. The point of 
attack being iinderground, the infected trees are commonly un¬ 
noticed until they begin to fail. This stage may be recognized 
by the weak growth and yellow appearance of the foliage. 
The pictures in this bulletin give a good idea of the appear¬ 
ance of crown gall. Plate I. shows an extreme case of the dis¬ 
ease as affecting a six-year-old plum tree. This tree was un¬ 
doubtedly attacked in the nursery, and the continued growth of 
the gall so interfered with its nutrition that it was able to make 
but a feeble growth and was nearly dead when it was dug. Plate 
II. is from a photograph of a peach tree, showing a large gall on 
the roots and a somewhat unusual case of the development of 
galls on the trunk above ground. Plate III. shows badly diseased 
apple trees just as they were received from the nursery. 
This disease first began to attract the serious attention of 
Experiment Station workers in 1892, when the California station 
published a bulletin on the subject. This was followed by a 
number of articles from different Experiment Stations, but it was 
not until 1900 that any definite knowledge of the disease was 
gained. During this year Prof. Tourney, of the Arizona Experi¬ 
ment Station, published a bulletin, in which he proved that crown 
galls on almond, apricot and peach trees are produced by the irri- 
