BLACKSPOT CANKER OR APPLE TREE ANTHRACNOSE. 



By W. H. Lawrence, Plant Pathologist and Horticulturist for Hood 

 River Apple Growers, Hood River, Oregon, and County 

 Fruit Inspector' for Hood River County. 



More than a decade has passed since the disease of the apple tree 

 earlier known under a variety of names as canker, black canker, black- 

 spot canker, blackspot apple canker, blackspot, deadspot, apple tree 

 anthracnose, sour sap d.sease, now widely known as blackspot canker 

 or anthracnose, made its appearance in apple orchards in various pjaces 

 throughout the Pacific Northwest. In the face of the fact that the 

 disease is one of the most destructive of all the fungous disease of the 

 apple throughout the sections in which it occurs, there are orchards in 

 all of the localities that do not receive the proper attention to control 

 the disease, principally due to neglect on the part of the orchardists, but 

 also in part due to a lack of interest in the business or ignorance or both. 

 Were it true that this disease had proven to be an extremely diffieult 

 one to combat, there would be some excuse for the presence of trees 

 well plastered with cankers and in all conditions of health from the 

 apparently healthy to the weak one loaded with a füll crop of slowly 

 developing apples — last effort to reproduce its kind before its death. 

 Since this is the easiest to control of all of the diseases of the app'je 

 induced by a fungus, there can be no explanation other than neglect or 

 indifference on the part of the person in charge of the property. The 

 fact that the trouble has continued year after year, causing more or 

 less damage, has been an incentive for studying this disease. Enough 

 has been learned to appreciate how destructive the fungus causing the 

 disease really is, and that the problem of its control or eradication is 

 far more important than suspected at an earlier date. 



Briefly stated, the history covering these investigations gives to 

 Professor A. B. Cordley of the Oregon State Experiment Station, credit 

 due him for investigations proving the relation of the fungus which he 

 gave the name gloeosporiiim malicorticis, to the disease termed apple 

 tree anthracnose. The writer later studied this disease with particular 

 reference to cankers occurring on other trees and the fungi causing 

 decay of apples placed in common storage. The fact that the fungus 

 will attack the prune, plum and pear, causing surface cankers; will 

 attack the cherry causing gummosis, and also causes a serious rot of 

 apples in common storage, was established. The results of these studies 

 were published in Bulletin 66 of the Washington Experiment Station 

 under the title of Blackspot Canker, a name in keeping with the names 

 in common use in the section in which the study was made as well as 

 being a good descriptive name. More recently Professor H. S. Jackson 

 of the Oregon Agricultural Experiment Station has proven that the 

 fungus causing this disease, has, like many other well known forms of 

 fungi, an ascigercus or perfect stage as well as a conidial or summer 

 stage. 



This fact has a very important beai'ing on the late investigations 

 made on this disease by Mr. B. B. Pratt of the Bureau of Plant Industry 



