186 CROWN-GALL OF PLANTS. 



He also cites from a correspondent as follows: 



It is more prevalent in apple than in anything else. On the block of apple trees 

 which were 2 years old when you were here, we did not find a single tree affected, 

 while on our trees, now 2 years old, we find 30 to 40 per cent affected with crown- 

 gall and we will sustain a big loss. At the time these 2-year trees were grafted, I 

 grafted 30,000 for a neighbor for his own orchard planting and on the trees taken up 

 he has found but 2 or 3 per cent affected, though the source of stocks and grafts was 

 the same. This looks as if the disease was in my ground. 



The conclusion of this nurseryman is entirely correct ; the cause of 

 the disease is in his ground. 



A former colleague, Mr. P. J. O'Gara, who has had a very wide 

 experience on the Pacific coast, has observed the disease to be seri- 

 ously injurious to Spitzenberg apples in Oregon, and also to pears, 

 dwarfing the trees and reducing the size of the fruit. He states that 

 hold-over blight (Bacillus amylovorus) is very apt to find lodgment 

 in the galls when they occur above ground and that root-rot begins 

 commonly in the galls when they are underground (oral communi- 

 cation). He is also our authority for the statement that crown-gall 

 has seriously injured peach growing in Colorado. The disease seems 

 to be worse in dry climates, where irrigation is practiced. 



In 1910, after conversation with Mr. O'Gara, the following letter 

 was received from him: 



I am inclosing a photograph of crown -gall (hairy -root type), taken in my office at 

 Medford, Oreg. This tree is 7 years old, but is no larger than a good 3-year old and 

 certainly not so vigorous. This tree is exactly like 50 trees in the same apple orchard, 

 the variety being Esopus Spitzenberg. Crown-gall, either hairy, hard, or soft types, 

 certainly injures apples if the infection starts with the seedling or the graft. If a tree 

 is several years old before becoming infected, serious injury is not so liable to be the 

 case, as the vigor of the tree somewhat counteracts the effects of the gall. But Spitz- 

 enberg apples infected on bodies or crowns often become so ' ' warty " that growers 

 cut them out. Besides, crown-gall above the ground always permits the entrance of 

 fungi, and in susceptible varieties like Spitzenberg, Bacillus amylovorus gets in its 

 deadly work through the gall. Anyone having experience on the Pacific coast knows 

 that a crown-gall above the crown of a Spitzenberg means blight infection sooner 

 or later. 



Later Mr. O'Gara sent on a blighted apple limb from ]\Iedford, 

 Oreg. (PI. XXXI), with the following note: 



I am sending you under separate cover a specimen of Spitzenberg apple limb 

 which has a bad crown-gall, through which pear blight infection entered. Crown- 

 gall on the body or crown of a Spitzenberg apple is very dangerous, from the blight 

 standpoint. The past year I have seen hundreds of blight infections through these 

 galls. For this reason every cro\\Ti-gall must be removed, and our inspectors enforce 

 this regulation to the letter. 



In 1898 Selby cited the case of a grower of nursery stock who 

 found part of a block of apple trees badly affected with gall about the 

 year 1893. The trees were dug up and the ground left to rest a year, 



213 



