6 MANUAL OF FRUIT DISEASES 
spots may fuse and frequently the leaf is killed. In case of 
severe infection defoliation may result. On the blossoms the 
lesions are found chiefly on the pedicels and calyx. The oliva- 
ceous spots may encircle the slender stalk as a result of which 
it withers and 
ultimately falls, 
thus reducing the 
set of fruit. 
Blossoms which 
show even a sin- 
gle lesion seldom 
hang to the tree. 
The petals are 
never affected. 
Mature scab spots 
on the fruit are 
very similar in 
size, shape and 
color to those on 
the upper leaf- 
surface, although 
at first they are 
smaller and more 
sharply defined. 
f They are usually 
: most numerous 
Fic. 1.— Apple-scab on leaves; types of infection on 
upper (left) and lower (right) surfaces. about the blos- 
som-end (Figs. 2 
and 3) of the fruit, due to the fact that infection occurs largely 
in the spring while the young apples still remain in an upright 
position (Fig. 4). The lesions on the fruit show a whitish, 
papery margin, often very wide; this is the undissolved cuticle 
which has been slightly uplifted by the pathogene advanc- 
ing at the edge of the lesion (Fig. 2). As the spots grow 
