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-BiicHT 
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, Angouléme 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 
