White pine weevil

The White pine weevil (Pissodes strobi) is a notorious forest pest belonging to the family Curculionidae and the order Coleoptera. It is widely recognized as the most serious insect pest of terminal shoots of young coniferous trees, significantly impacting plantation growth and timber quality throughout its native range.

Its primary hosts include various species of spruce and pine. The pest is particularly attracted to trees that have recently established a vigorous terminal leader, making young plantations especially vulnerable to infestation during their most critical growth phases.

The life cycle is generally annual. Adults overwinter in the soil or forest litter, emerging in early spring to feed and mate. Females lay eggs in small punctures created in the terminal shoot. Upon hatching, the larvae mine downward under the bark, girdling the stem and disrupting the movement of water and nutrients, which inevitably kills the leader.

The most visible symptom of an infestation is the drooping of the terminal shoot, often described as a "shepherd's crook." Once the terminal leader is killed, the tree loses its straight form, as lateral branches compete to become the new leader, resulting in "cabbage-like" deformity or a crooked stem, which severely degrades the wood value.

Effective management strategies include cultural, biological, and chemical methods. Cultural practices involve pruning and destroying infested leaders before the new generation of adults emerges. Chemical control typically relies on systemic insecticides applied to the terminal leader in early spring. Maintaining ecological diversity in forest stands can also help suppress populations of this damaging weevil.