328 MANUAL OF FRUIT DISEASES 
fection-courts the bacteria multiply rapidly and within a 
few days infection results. The first evidence of the disease 
in the spring is blossom-blight, the tender tissues of the 
blossom and of the embryo fruit being killed suddenly. The 
bacteria in a blighting blossom are carried from it to other 
blossoms by insects, especially bees, and so the pathogene 
spreads through the orchard, and from one orchard to another. 
From the blossoms the 
bacteria work their way 
down the pedicel to the 
‘spur, killing the bark 
and causing the leaves 
as well as the blossoms 
to wither. The leaf- 
tissues are not usually 
invaded. From _ the 
spur the bacteria may 
pass to the other healthy 
pedicels of the cluster 
and finally enter the 
fruit through its base. 
Fruit-blight may also 
arise by the bacteria 
Fic. 89.— Oozing fire-blight canker. Note being deposited in 
drops of exudate. wounds made by the 
curculio and other in- 
sects (Figs. 90 and 91). The bacteria are similarly introduced 
into the growing tips of twigs and watersprouts by aphids, twig- 
blight resulting. Affected twigs emit the ooze which serves as a 
source of inoculum for other twigs, shoots and blossoms. In 
most varieties of pears, twig-infection, unless removed, is 
inclined to continue down the main limb and even into the body 
of the tree. Watersprouts frequently mark the center of a 
canker, indicating the manner of entrance of the bacteria. 
