Blight Canker of the Apple Tree. ' 213 



opinion that many of the trees in the Hudson River vahey and about 

 KirkviUe were cankered prior to the winter of 1902-3. The severe 

 weather no doubt weakened the trees yet free from the disease, thus 

 rendering them more susceptible to attack during the summer of 1903. 

 It also further weakened the trees already affected, rendering their de- 

 struction from further growth of the cankers certain. The appearance 

 of a large number of the cankers in 1904 showed clearly that they had 

 originated in 1903 ; others gave evidence that they had originated prior 

 to that time ( Fig. 54). The w^inter of 1903-4 was also a severe one and 

 no doubt added to the sum of the injury already produced. To just 

 what extent the winter injury in this section is responsible for the death 

 of the trees is a question. In certain cases it was very evident that the 

 tree had died from this cause. Such injuries were easily distinguished, 

 however, from canker spots. That these dead spots on limbs and body 

 and in the crotches resulted from freezing is, to say the least, exceedingly 

 improbable. I base my opinion on the following facts : 



(i ) The cankers may appear on any side of the body or main limbs ; 

 (2) The spots are usually more or less circular or oval with sharply de- 

 fined margins; (3) The cankers are in practically every case formed 

 about the base of a shoot or about a wound of some sort ; (4) Every indi- 

 vidual canker whose entire history is known was observed first to appear 

 during the warm weather of spring or summer; (5) Typical cankers have 

 been observed to form about the base of young sprouts wdiich have been 

 twig blighted; (6) Typical crotch cankers appeared during the past sum- 

 mer in trees which throughout the spring and early summer appeared to 

 be perfectly healthy; (7) The bacteria of pear blight have been found 

 repeatedly in the tissue of actively spreading cankers; (8) Spots, to every 

 appearance exactly like typical cankers, were produced in the bark of 

 healthy trees by inoculation with blight bacteria. 



Ciiltiz'ation. — It is known that well cultivated pear trees suffer more 

 severely from " fire blight " than do those not so treated. Constant culti- 

 vation results in rapid growth and consecjuently succulent tissues, which 

 are most favorable for the development of the blight bacteria. My ob- 

 servations seem to show that the same thing is true as regards the canker 

 form of the disease in the apple tree. A number of young orchards were 

 visited that had received little or no cultivation since setting and had 

 consequently made a much slower growth than cultivated ones of the same 

 age. They were, however, remarkably free from cankers, although not 

 entirely so. In one orchard visited, it was noticed that three or four rows 

 of trees at one end were practically free from the disease while the re- 

 mainder had nearly all died from its effects. Inquiry brought out the fact 

 that these few rows had received but little cultivation while the remainder 

 of the orchard had the best of care in this respect. 



