344 BULLETIN 226. 



to nearly half an inch in diameter. The brown rot of stored apples is 

 also due to the same fungus. 



Cause. The cause was not known until about six years ago, when it 

 was worked out by Wendell Paddock of the Geneva station.* Until that 

 time it was commonly attributed to sun-scald. Comparatively few fruit- 

 growers are yet informed of the real cause. It is still attributed to sun- 

 scald or lightning, or passes as " dead limbs " without any cause. Prac- 

 tically no sun-scald has been seen in either of the counties studied. 



Mr. Paddock found that the canker is caused by a fungus that grows 

 on the bark and cambiumf layer of the tree. The black color of the 

 canker is partly due to the spore-fruits of the fungus. Many of the 

 spores (seeds) remain on the branches till spring or longer, when they 

 are given off and disseminated. The fungus seems to be unable to pene- 

 trate to the cambium layer through living bark. The cankers are thought 

 to be formed by those spores that chance to fall in some slight wound 

 and there germinate and produce more cankers. Sometimes the. fungus 

 grows for some distance on the outer bark without penetrating to the 

 cambium. (See B, Fig. 86.) In such cases no direct injury is done to 

 the tree, but spores are produced and disseminated so that a constant 

 source of infection is maintained. 



Treatment. With the exception of the Twenty Ounce, no orchard in 

 which the trees have always been kept in a good growing condition has 

 been found to be seriously affected. Something more than thrifty growth 

 seems to be necessary in order to prevent the destruction of the Twenty 

 Ounce. 



A few farmers in Wayne county and more in Orleans county have been 

 treating the disease during the past few years and have had excellent 

 results. The essential points of the treatment are : 



(1) Prune out the limbs that are badly diseased. 



(2) Spray the limbs with Bordeaux mixture. 



(3) Most important of all, get the trees to growing. 



Mr. G. D. Simpson of Carlton has carried the treatment a step farther. 

 When pruning he scraped off the rough, diseased bark around each 

 canker and gave a generous application of strong blue vitriol. This was 

 undoubtedly a good thing, but the treatment given above seems to be 

 invariably successful. 



*New York Agricultural Experiment Station, Bulletin 163, Dec., 1899. 

 fThe cambium layer is a tissue that lies between the wood and the bark. It is the 

 tissue that produces the new wood and inner bark. 



