CHAPTER XI 

 PEAR DISEASES 



THE most injurious diseases affecting the pear are fire-blight 

 (page 323) and scab (page 332). Fire-blight is commonly 

 found on the apple and quince, and on these three fruits great 

 damage may be wrought. Pear-scab is peculiar to that fruit ; 

 it is not the same disease as apple-scab, in spite of the popular 

 notion which prevails in the affirmative. Less prominent dis- 

 eases, like pink-rot, superficial bark-canker and leaf-blight, are 

 also found on the apple and quince. 



FIRE-BLIGHT 



Caused by Bacillus amylovorus (Burr.) Trev. 



This disease is known to affect several fruit-trees and a few 

 ornamentals belonging to the apple family. The discussion 

 presented here concerns only the pear. 



All varieties of the pear are more or less susceptible to fire- 

 blight. But it is generally believed that the Bartlett, Flemish 

 and Clapp Favorite are more frequently and more severely 

 attacked than the Kieffer, Angouleme and Seckel. However, 

 these apparent variations in resistance may not be traced to an 

 inherent difference among kinds of pears, but to other factors 

 and conditions frequently overlooked. The presence of the 

 disseminating agents (insects), the source of the inoculum, 

 and the period of growth-activity of the host rule the situation 

 more than real immunity. 



The disease is very generally known as fire-blight. It is also 



323 



