What is pear leaf blister mite?
Pear leaf blister mite is caused by the gall mite Eriophyes pyri, a small (0.2 mm length) pest that causes pink-red blisters that appear on young pear leaves in spring. The leaves tend to curl, and the blisters gradually turn black. Fruit may be distorted and fall early.
Mature females overwinter at the base of buds on pear trees or in nearby hedges (hawthorn and mountain ash are two other host plants), and lay eggs within leaf and fruit buds in spring. Adults hatch after 20-30 days, and start feeding on the young leaves, causing blistering.
Several generations of the mite develop every season, and they can migrate to other leaves, and even to other pear trees, possibly transported by wind, birds or insects. Pear leaf blister mite can affect any pear trees, but particularly trees that are suffering drought stress.
How to control pear leaf blister mite
Ensuring that your trees never go without water is the best way to prevent pear leaf blister mite. Before planting, add organic material, such as farmyard manure, to the soil. Place a layer of mulch around the trees to maintain soil moisture. Water the trees in drought conditions.
If just a few leaves are affected, remove them and dispose of them definitively. If the whole tree is affected, wait until November/Dececember, gather up all infected leaves and remove from the garden. If the tree is planted close to a hedge, consider transplanting it to another location (this can be done in December/January).