THE MONTHLY BULLETIN, 331 



blossom rot. A characteristic gumming appears on the infected spurs. 

 A few cases have been noted where the infection continued some 

 distance into the bark of the branch from which the spur grew, causing 

 an area of dead gumming bark — a canker we might call it. This has 

 been noted in connection with both the blossom rot and brown rot. 

 A few cases have been observed where infection had apparently worked 

 into large branches from a brown rot mummy resting against them. 



For some years the writer has noticed a close correspondence in the 

 infection period for the blossom rot and the appearance of certain 

 sour sap conditions in apricot trees throughout the valley. During 

 1914, and the present year, there were peculiar weather conditions 

 favorable to the fungus, which caused two periods of infection of 

 the blossom rot — the first when the fruit was the size of buckshot — the 

 fore part of March, 1914 — and the second when about the size of 

 marbles — the fore part of April, 1914. Corresponding to each of these 

 periods there developed cases of sour sap or gumming conditions in 

 the apricot trees, especially in young orchards — one to five years old — 

 and in newly transplanted nursery trees. During the first infection 

 period the late nursery shipments of apricot trees contained large 

 numbers of trees with soured areas of bark. The affected areas on 

 this nursery stock and on young orchard trees are remarkably similar 

 in appearance to the affected areas on fruit spurs as above noted, and 

 to artifieiall}^ produced cankers as described below. 



The infected area may occur anywhere from the roots to the 

 topmost branches. The origin of the infection can often be traced 

 to a bruise, a cut or other injury. The infection proceeds both up and 

 down the branch or tree. If the diseased area does not extend down 

 as far as the graft, the tree can be cut off and a new trunk started 

 without recourse to grafting. This operation has been successfully 

 performed on scores of young trees. In a few instances where the 

 infection was confined to one side, the infected area was cut out and 

 disinfected, and the injury soon healed over. In several cases this 

 operation was successfully performed on large trees in Avhieh cankers 

 extended one to two feet along the limb, the width being two to five 

 inches. Infections, sometimes similar in appearance to these cankers, 

 also frequently follow large untreated pruning wounds. 



To test the possibility of gummosis, or of certain kinds of "sour 

 sap," being produced by the same organisms which cause blossom rot, 

 six inoculations were made, using a thin slice from a decaying green 

 fruit for inoculating material. This was on April 10, 1914. All six 

 inoculations developed gumming conditions within a few days and soon 

 large gumming cankers were in active growth. Check incisions pro- 

 duced no diseased conditions. The active development ceased in the 

 course of a month or two. The inoculations were made on branches 

 from two to six inches in diameter. The largest canker was about two 

 inches wide and eight inches long when it was excised, to prevent the 

 possible destruction of the branch. 



On April 16, 1914, another experiment was tried on one-year old 

 trees, using thin slices of diseased bark from another tree of the same 

 age which had begun to "sour" at a break in the trunk caused by the 

 plow team. Two limbs, about an inch in diameter on each of two trees, 

 were inoculated. These developed typical cases of gumming. Ojie 



