Poplar gall mite

Systematic position. The poplar gall mite (Aceria parapopuli) is a member of the Eriophyidae family within the order Acariformes. These are microscopic arthropods that induce specific hormonal changes in host plants, resulting in the formation of abnormal growth known as galls.

Host plants and damage symptoms. This pest primarily attacks various species of poplar, such as Populus deltoides and Populus nigra. The mite causes the formation of woody or spongy galls, ranging from small nodes to large, tumor-like structures, usually found on petioles, twigs, and buds. These growths significantly alter the appearance of the tree.

Biology and life cycle. The mites overwinter as adults, hiding within bud scales or bark crevices. In spring, as temperatures rise and the sap begins to flow, the mites emerge and start feeding on developing shoots. Their saliva contains chemicals that disrupt normal cell division, creating protective galls. Several overlapping generations occur during a single growing season.

Economic impact. The poplar gall mite is primarily a significant pest in nurseries, parks, and urban landscapes. Heavy infestations can lead to stunted shoot growth, distorted branches, and a general decline in the tree's vigor. While rarely lethal to mature trees, the aesthetic damage and increased susceptibility to secondary infections make management essential.

Protection and control measures. Controlling Aceria parapopuli is challenging because the mites reside protected inside the galls for most of their lifecycle. Effective management includes:

• Regular pruning and removal of galled branches during the dormant season.
• Sanitary disposal of infested plant material by burning.
• Systemic acaricide applications timed with bud burst in early spring.
• Promoting tree vigor through proper irrigation and fertilization to minimize stress.