176 State Horticulturhl Society. 



or bruises on the limbs and bodies of trees. These wounds, commonly 

 known as "barking," may be made by careless workmen in plowing or 

 working about the trees or from the gnawing of animals, one of the 

 worst of which in New York is the wood-chuck. A large percent of 

 such wounds heal eventually, but frequently, through the agency of in- 

 sects or other means, these wounds serve as infection courts for the canker 

 bacillus. An interesting wound infection came under my observation this 

 season. In cutting a cankered branch from a tree I accidentally "barked" 

 a large limb with the freshly cut end of the diseased branch. I thought 

 little of it at the time, but returning to the tree later to get material for 

 cultures from the diseased stub, I was delighted to find on the wounded 

 limb about the abrasion a large and actively spreading canker. 



I believe that insects are responsible for a large number of infections, 

 especially those on the bodies and in the crotches of the limbs. To prove 

 this in most cases is quite a task, to say the least. A large number of the 

 cankers, especially at the bases of the trees, did not seem to have had their, 

 origin either in a bruise or from a blighted water-sprout. I was con- 

 vinced that the puncture of insects was responsible for the infection. 

 As I went from tree to free one day on my weekly inspection, the proof 

 of this conviction was presented to me. You can see the hole made by 

 the insect and surrounding it the well marked boundaries of a recent 

 canker. Whether the borer itself caused the infection or whether it was 

 brought later by flies that came to feed on the exuding sap, cannot be 

 said. In either case it was the borer that afforded the infection court. 



As a general deduction then it may be said that infection occurs only 

 through a wound of some sort. Moreover I believe that the infection 

 court must be of such a nature that it will not dry out quickly. An abund- 

 ance of moisture is known to be necessary for the rapid development of 

 the blight organism. This was repeatedly demonstrated in the large 

 number of pure cultures which I had under observation during the sum- 

 mer. The growth was most abundant and vigorous in liquid media. 

 Where the diseased tissue of freshly spreading cankers was cut out with 

 a knife and the wound exposed without any other treatment, the canker 

 ceased to spread and the place healed rapidly. 



We now come to the portion of the subject that is of especial interest 

 to the grower, and which to him is the end and aim of all investigations 

 into the nature of the disease, namely, the means of combatting it. Any 

 intelligent treatment of a disease depends upon a more or less complete 

 knowledge of the nature of the organism causing it. The work of the 

 past year has, therefore, been devoted almost entirely to a study of the 

 phenomena exhibited by the disease and the cause of the same. I have. 



