New York AGRICULTURAL EXPERIMENT STATION. 315 
NATURE OF INJURIES TO FRUIT TREES. 
Mite work on pear leaves— The galls first appear as minute 
greenish pimples with a more or less reddish tinge, which are barely 
distinguishable from the leaf. With increase in size they become 
reddish, often causing brilliant colored spots on the leaves, and 
later, with the drying up of the diseased tissue, turn to a dark 
brown or black. On the under surface of the leaf, the affected 
areas are corky and raised, with the epidermis rather loose and 
wrinkled, suggestive of a blister, hence the popular name apple 
and pear blister to designate the work of the mite. Leading into 
each spot there is usually a tiny opening. ‘The galls are irregular 
in shape, and vary in size, according to age, the largest being about 
one-eighth of an inch in diameter. Sometimes they lack red and 
differ little from the general color of the leaf. Some varieties of 
pear, especially the Keiffer, when much infested, have the unfolding 
leaves completely reddened, swollen and blistered, which, when 
unfolded, become ‘much wrinkled and unshapely. The galls are 
usually arranged in a row on each side of the main rib. This group- 
ing of the affected areas seems to be determined by the pubescence 
of the leaf and the condition of the leaf when unfolding, at the 
time of the migration of the mites from under the bud scales to 
the expanding leaf. When numerous, the spots may coalesce, form- 
ing dark brown or blackish patches of various sizes which may 
cover much of the leaf and cause it to rupture in one or more parts, 
especially along the margins. Severe infestation of the mites may 
cause more or less defoliation, resulting in the premature falling 
of the fruit from the most injured leaf clusters. The mites also 
cause light colored pimples about the calyx of the frit and on the 
fruit stems, but these injuries are occasional and do not appear to 
impair the health or the value of the fruit. 
Mite work on apple leaves— The work of the mite on apple first 
shows on the upper surfaces of the leaf as distinct light colored 
pimples and on the undersides as blisters or thickened areas of the 
same color as the leaf. The affected areas are of irregular size and 
are unevenly distributed, though the larger proportion of them are 
about the sides and the base of the leaf. Some of the blisters may 
have a reddish tinge, somewhat similar to the pear leaf galls but 
ordinarily of a less brilliant color. As the galls become older they 
