Pear Leaf Blister Mite

Have you ever seen weird crusty growth on your pear tree’s leaves? You might be seeing the damage caused by pear leaf blister mites. These creatures are distantly related to spiders; they are arachnids, a group which includes spiders, mites, scorpions, ticks, vinegaroons, harvestmen, pseudoscorpions, and camel spiders.  What they have in common is eight legs (unless they have fewer!), no wings or antenna, and most are carnivorous though ticks and some mites can be parasites.

The pear leave blister mite is one of these parasites, causing galls on pear leaves that look like roughened tissue. These “blisters” start out green and then turn dark brown to black.  The mites’ feeding causes the growth of blisters, which the mites then use as protective cover. They overwinter beneath the protective scales covering leaf and fruit buds and begin feeding on leaves and blossoms as they open.  

In most cases, the mites are restricted to a small part of the canopy and do not cause serious problems.  They have a number of natural predators, including other (predatory) mites, a tiny species of ladybird beetle, and certain thrips insects.  By avoiding the use of broad-spectrum insecticides on pear trees, these natural allies can do their work. If the problem is severe enough, consider an autumn spray with horticultural oil after the leaves have fallen – concentrate on the small diameter twigs where they will be overwintering. As always, Legacy Tree Company can help maintain your trees’ health – give us a call!

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