Spruce resin midge

Systematic position. The spruce resin midge (Resseliella ingrica) belongs to the order Diptera and the family Cecidomyiidae. This small insect is a significant pest primarily affecting various species of the genus Picea (spruce), causing physiological damage to the host trees.

Host plants and damage symptoms. The primary hosts are spruce trees, where the larvae feed on the cambium and inner bark. The most distinct sign of an infestation is the production of copious amounts of resin (sap) on the bark, which solidifies into visible, often unsightly, resinous patches on the tree trunk.

Biology and life cycle. The life cycle is closely synchronized with the spruce tree phenology. Adult midges lay their eggs in bark fissures or wounds. Upon hatching, the larvae penetrate the bark layers. They feed throughout the growing season, and in many regions, the larvae overwinter in the soil or within protected spots under the bark before pupating in the spring.

Harmfulness. The damage is cumulative. By destroying the cambium, the larvae disrupt the tree's vascular system, hindering the transport of nutrients. This stress weakens the spruce, making it susceptible to secondary pathogens and opportunistic bark beetles, which can eventually lead to the decline or death of the tree.

Protection measures. Managing this pest requires an integrated approach to forest and garden health:

• Regular monitoring of tree trunks for early signs of resin flow.
• Removal and proper disposal of heavily infested, dying trees to reduce the pest population.
• Application of appropriate insecticides during the adult flight period if infestations are severe.
• Promoting tree vigor through balanced fertilization and adequate water management.