Plum leaf gall mite

The plum leaf gall mite (Eriophyes similis) is a member of the Eriophyidae family, known as gall mites. These are microscopic organisms that do not have wings and rely on wind or insects for dispersal, making them a challenging pest to manage once they have established themselves within an orchard environment.

This mite primarily attacks stone fruit trees, with the plum tree being its most common host. The pest induces the formation of characteristic galls on the leaves, which serve as a protected environment for the mites to feed and reproduce, sequestered away from most external environmental influences.

The life cycle begins with overwintering females hiding under bud scales. As temperatures rise in spring, they migrate to the developing leaf tissue. As they feed, they secrete chemicals that cause the leaf to produce outgrowths or 'pockets', inside which the mites dwell throughout the summer months.

The damage is mostly cosmetic but can be severe in high-density populations. Heavy infestation leads to leaf curling, premature browning, and reduced photosynthetic efficiency. This weakened state of the foliage contributes to poor nutrient storage, which eventually affects the tree's vigor and fruit quality.

Management strategies focus on reducing the overwintering population. Mechanical methods, such as pruning and burning infested plant parts, are highly recommended during the dormant season. Chemical control with acaricides is most effective in early spring, precisely when the mites are migrating from the buds and are exposed to treatment applications.