GENERAL APPEARANCE OF INJURY. 



The casual observer who has had little experience with the disease will 

 probably first notice its attack iu the spring about the time growth starts 

 or a little later. It will then appear as an oval-shaped spot of varying size 

 on the bark, slightly sunken generally with a smooth surface. It is seldom 

 found in older trees where the bark has become corky. This spot most likely 

 had been attacked some time during the last two or three months of the 

 previous year, and had been gradually developing to its present stage. If 

 the tree had been carefully examined during the winter, when the disease 

 was in its first stage, it would appear only as a slight discolouration of the 

 bark, generally quite rounded, and on cutting into the spot it would be 

 soft and of a slimy nature. As the period since attack lengthens, the 

 cankered area becomes more sunken, firmer, and darker in colour. Increase 

 in size is seldom noticed after the middle of May. During the late spring 

 and summer months the face of the canker will become quite rough and 

 with uneven, raised pustule-like bodies. The edge of the wound will often 

 break away from the surrounding wood, which will begin to callous around 

 it. The following winter or year the canker often breaks away entirely 

 from the limb, leaving the wood bare, with the healing process taking place 

 from the edge of the wound. This leads us to believe, from field studies 

 of the disease, that, the canker is only of one season's duration and requires 

 reinfection yearly to carry on the disease, and this factor, providing other 

 conditions were the same, makes the disease more easily controlled than if 

 it had been perennial in the host. 



The fruit is also attacked, and the work of the pest has been noticed 

 principally in apples in storage. Prof. Lawrence, of the Western Washington 

 Experimental Station, reports that he has transferred the disease to the 

 trunk and limbs by inoculation from the diseased fruit. Where fruit is being 

 stored, care should be taken to have storage conditions right (cool and dry) 

 to prevent the spread of the disease. In the orchard the work of the fruit- 

 grower should be directed towards controlling the disease on the tree, as if 

 controlled there it destroys the only possible means of fruit infection in the 

 orchard. 



CAUSE OF INJURY. 



Numerous theories have been advanced as to the cause of the disease. 

 Frost injury, winter injury, and sour-sap have been frequently given in the 

 past, but it has been definitely proved it is due to a parasitic fungus. It 

 will not be necessary to discuss here the technical methods used to associate 

 the disease with the fungus, as the majority of fruit-growers are satisfied 

 provided they have a working knowledge of the disease. Suffice it to know 

 that it. is caused by a parasitic fungus termed Mncrrtphoma curvispora by 

 ('. II. 1'eck, and (llnoximriiini iniilicnrticix by A. B. Cordley. and black-spot 

 canker, apple-tree anthracnose. etc., by the fruit-grower. 



What is a fungus? This is possibly the first question that will arise 

 in the mind of the fruit-grower when he is approached by the Orchard 

 Inspector, who informs him that his trees should be sprayed for apple-scab, 

 black-spot canker, shot-hole fungus, or some other fungous disease. It might 

 lie termed a degenerate plant, in that it is a plant living as a parasite or as 

 a saprophyte, or in conjunction with some other plant, and belongs to the 

 plant kingdom. It is a microscopic plant. Most of us have seen the mould 

 that starts on damp bread. This is a fungus. The white thread-like growth 



