112 MANUAL OF FRUIT DISEASES 
apple, but from many other plants, including the almond, apricot, 
beet, blackberry, cherry, chestnut, clover, cotton, daisy, English 
walnut, grape, honeysuckle, hop, lettuce, peach, plum, poplar, 
potato, prune, quince, rose, tobacco, tomato, turnip and willow. 
This list is incomplete but will give an idea of the wide range of 
plants susceptible to the disease, and therefore of the many 
sources from which the bacteria may come to the apple. 
Control of crown-gall. 
In dealing with crown-gall, the following points should be 
borne in mind: (1) the great number of plants attacked; 
(2) the identity of the bacteria causing hairy-root and crown- 
gall; (3) the greater abundance of the disease in nursery-stock ; 
(4) the bacterial nature of the disease; (5) the entrance of the | 
pathogene into the host through wounds; (6) its presence in the 
soil; (7) the distribution of the pathogene in nursery-stock; 
(8) internal infection by tumor strands, and that therefore not all 
galls necessarily arise from an external source. In the light of 
these data the following measures and precautions should be 
employed: (1) deep planting to protect the plant against 
frost-injury ; (2) avoid injuries to the roots and stems; (3) re- 
move diseased trees; gall excision is unsatisfactory and un- 
reliable; (4) protect grafts at the point of union by using a 
root and scion of approximately the same size, and by wrapping 
them carefully; (5) reject diseased nursery-stock. (See Table 
of Contents for other fruits which are affected by crown-gall.) 
REFERENCES 
Smith, E. F., Brown, N. A., and Townsend, C. O. Crown-gall of 
plants: its cause and remedy. U. S. Agr. Dept. Plant Indus. 
Bur. Bul. 213: 3-215. 1911. 
Smith, E. F., Brown, N. A., and McCulloch, L. The structure and 
development of crown gall: a plant cancer. U. S. Agr. Dept. 
Plant Indus. Bur. Bul. 255: 3-60. 1912. 
Swingle, D. B. Fruit diseases in Montana. Crown-gall of apple. 
Montana Agr. Exp. Sta. Cire. 37: 290-301. 1914. 
