Lime leaf gall mite

The lime leaf gall mite (Phytoptus canestrinii) is a microscopic herbivorous mite belonging to the family Phytoptidae, order Trombidiformes. This species is highly host-specific, primarily infesting various species of linden (Tilia) trees.

These mites affect the health of linden trees by colonizing the leaf surfaces. While they are usually considered pests of secondary importance, heavy infestations can significantly affect the aesthetic value of street trees and park landscapes, leading to premature foliage drop.

The biology of the mite is synchronized with the tree's growth. Adult females overwinter in bark crevices, under bud scales, or in the soil near the trunk. In early spring, they migrate to the developing leaves, where their feeding triggers the formation of leaf galls.

The characteristic damage caused by the mite is the appearance of galls—abnormal swellings on the upper surface of the leaves. The corresponding underside of the leaf shows depressions filled with a dense, felt-like mat of plant hairs, which provides the mites with a protected environment to feed and reproduce.

• Development of felt-like patches on the underside of leaves.
• Distortion of leaf tissues and discoloration.
• Reduction in overall tree vigor and photosynthetic efficiency.
• Requirement for systemic or contact acaricides during early spring.

Control strategies involve the application of registered acaricides early in the season, specifically targeting the period when mites emerge from their overwintering sites before the galls are fully formed. In severe cases, promoting tree health through proper irrigation and fertilization is essential to help trees tolerate and recover from mite infestations.