PEAR DISEASES 329 
Suckers which arise from 
the crown, at or below 
the surface of the soil, 
are often blighted, allow- 
ing the bacteria entrance 
into the bark of the roots. 
Trees may die from such 
aformofattack. Grafts 
are especially disposed to 
blight during the first 
year or so on account of 
their rapid and succu- 
lent ‘growth. Wounds 
in the larger limbs or 
the body of the tree — 
may serve as centers of 
1 
Fig. 90. — Fire-blight on apple fruit; drops 
of bacterial ooze on the surface. 
cankers. Here the bacteria are carried by the bark-boring 
beetle and deposited in their borings. In these cankers and 
Fig. 91. — Fire-blight on pear 
fruit; healthy fruit left, diseased 
fruit right. 
blighted limbs and twigs the bac- 
teria pass the winter. With the 
return of the warm weather and 
rains of the spring the rise of sap 
encourages the growth and multi- 
plication of the bacteria, which 
ooze out and afford the source 
of the inoculum for the opening 
blossoms. 
Weather conditions should not 
be confused with the causal factor 
of fire-blight. On the other hand, 
the weather is correlated to some 
extent with epiphytotics of the 
trouble. Late frosts may stop 
blight by killing certain of the dis- 
