308 PESTS OF ORCHARD AND SMALL FRUITS 
stop to the insect. Or the foliage may be sprayed with arsenate of 
lead as soon as the leaves are out. 
The Pear-leaf Blister-mite (Eriophyes pyri Pgst.) 
The leaves of apple and pear often are infested with a species of mite 
that burrows into the tissues of the leaf, causing a characteristic dis- 
coloration and swelling. Spots show in the upper leaf surface, at 
Fic. 470.— Work of the Pear-leaf Blister-mite. Original. 
first reddish, but later turning brown. At each spot the leaf is some- 
what thickened and its surface is slightly raised. Sometimes the fruit 
also is attacked and distorted. 
The mites themselves are very small. They hibernate under bud 
scales, migrating to the leaves as soon as the latter unfold, entering 
the tissue from the under side and feeding within. From time to time 
individuals come out and move to new places, starting additional 
colonies and causing a continual increase in the number of spots. In 
late summer they move back again to the twigs, hiding away for 
winter. 
