THE MONTHLY BULlETIN. 205 



DISEASE IN THE NURSERY. 



The disease is extremely common in the nursery. Peach on almond 

 rootstock is largely used, as the pits are easily and cheaply secured and 

 the root is well adapted to the various stone fruits. The amount of the 

 disease varies from year to year, being sometimes as great as 75 per 

 cent. The iMyrobalau plum is also a very popular stock on the Pacific 

 coast and is freer from gall in the nursery than the peach or almond. 

 There is no doubt that much of the disease among orchard trees has 

 its origin in the nursery, from which it is di.stril)uted over a great 

 range of territory. In California and other states where there is 

 rigid inspection of trees and plants, any showing these galls are rejected, 

 but often the infection has already taken place, but has not sufficiently 

 developed to show, and so passes inspection only to develop on the young 

 growing trees. 



The injurious effects of the disease vary on the different kinds of 

 trees, some readily succumbing to the disease, while others are more 

 resistant and may live and be quite productive for years. 



INFECTION AMONG ORCHARD TREES. 



Apple trees are quite subject to crown gall, especially at the point 

 w'here they have been bench-grafted. Here a gall often develops to con- 

 siderable size in addition to the healing callous. The infection enters 

 the injury from the soil. Budded or field-grafted trees, although more 

 expensive, are much superior for planting, as they are always freer 

 from crown gall. The hard and the soft forms of galls in apples have 

 a similar cause. The hard form is of slower growth and probably not 

 so injurious. Another form of apple disease supposed to have a cause 

 similar to crown gall is the hairy root disease. This disease is char- 

 acterized by an increased and abnormal production of fine roots that 

 differ from the normal fibrous ones. These abnormal roots can usually 

 be traced back to an irregular swelling or knot on the root. Prom these 

 w^arty knots a rapid-growing succulent root develops that by intricate 

 branching develops into a great mass of fine roots. Sometimes there is 

 a broom-like formation of fine roots that occurs at the end of a side 

 root that otherwise seems to be healthy. In general, the hairy roots 

 are more fleshy and numerous than normal roots. Some stages of the 

 disease are not accompanied by typical galls on the roots, but have 

 small enlargements of the tissue at the base of the clustered hair}- roots. 

 While this form of gall differs manifestly from the other one described, 

 it has been found to be caused by a bacterial organism closely allied 

 if not identical with the one causing the spherical galls. There is some 

 difference of opinion as to the seriousness of crown gall on apple, some 

 authorities claiming it does not injure the bearing properties, while 

 others claim a stunted and short-lived tree. 



Pears are occasionally diseased with crown gall and the pear stock in 

 common use, Primus communis, as well as the varieties so far tested, 

 readily take the disease. Not much is known as to how common or 

 serious the disease is in pears. 



Cherry stock is somewhat more resistant than peach or roots of the 

 other stone fruits. The jMazzard and Mahaleb roots when tested became 

 infected, yet the former variety showed considerable resistance. The 



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