The blister mite is a pest of foreign origin, that has been in the United States for many years. It was introduced into this country, probably from Europe, sometime before 1872, and by 1894 it was rather general in its distribution thruout the United States and Canada. At the present time this mite is a serious pest of apples in many of the fruit-growing sections of Western America. The blister mite was first reported in Utah by Hedrick as early as 1898. During the last few years it has been abnormally abundant in some parts of Utah.
Hawley, I. M., "Bulletin No. 197 - The Pear Leaf Blister Mite as an Apple Pest" (1926). UAES Bulletins. Paper 162.