Eriophyes pyri Pagenstecher
The pear leaf blister mite is widely distributed in the United States, but on the market the injury is found most often on fruits grown in the Pacific Coast States. The injury occurs sporadically when weather conditions delay the application of sprays in the orchard. Injured fruits are generally removed during packing, but a few may be overlooked. Bartlett is the most susceptible variety, but other smooth-skinned varieties such as Anjou and Comice are also affected. Varieties with naturally russeted skin, such as Bosc, Hardy, and Winter Nelis do not show the effects of blister mite attack.
Two types of injury by pear leaf blister mite are found oil pears: a diffuse russeting, usually most marked at the calyx end; and irregularly shaped, depressed russeted spots 1/8 to 1/2 inch across, most of which are eventually surrounded by a zone of almost decolorized skin (see photo). Severely damaged fruits may be misshapen.
The pear rust mite (Epitrimerus pyri Nal.) also causes russeting on pears. Severely affected fruits may be completely russeted, but the russeting on the calyx ends of slightly affected fruits may be confused with blister mite injury.
Mite infestations can be controlled by orchard sprays. The recommendations of the State agricultural extension service or experiment station should be followed.
Pear leaf blister mite injury