Elm bark weevil

The elm bark weevil (Magdalis armicollis) is a beetle species belonging to the order Coleoptera and the family Curculionidae. It is recognized as a significant stem pest that specifically targets elm trees (Ulmus spp.). These insects are characterized by their small size and distinct snout, which they use to feed on buds and delicate bark, as well as to prepare oviposition sites.

This weevil primarily infests elm species, showing a marked preference for weakened or stressed trees. Healthy trees are sometimes attacked, but the insects thrive in environments where tree vitality is low, such as areas affected by drought, soil compaction, or previous physical damage. High populations can lead to significant canopy decline and terminal shoot death.

The biology of Magdalis armicollis is linked to the development of larvae under the bark of branches and trunks. After mating, females bore holes into the bark to lay eggs. Upon hatching, the larvae tunnel into the phloem and cambium layers, creating intricate galleries. As they mature, they pupate within the wood, eventually emerging as adults through small exit holes in the bark.

Damage caused by this pest is twofold: adults cause superficial injury to twigs and leaves, while larvae cause structural damage to the tree's vascular system. This disruption of nutrient flow leads to branch dieback, yellowing leaves, and in severe cases, the eventual death of the tree. The presence of numerous tiny exit holes and sawdust-like frass on the bark is a diagnostic sign of an infestation.

• Sanitary pruning of infested and dead branches.
• Prompt removal and destruction of severely infested trees to prevent spread.
• Application of registered insecticides during the adult emergence period.
• Maintaining tree vigor through proper irrigation and soil management.
• Monitoring pest populations using pheromone or visual traps where available.