Seedling debarking weevil

  • Latin name: Hylobius congener Dalla Torre, Schenkling and Marshall
  • French name:
  • Order: Coleoptera
  • Family: Curculionidae
Description

Distribution

Canada

Damage, symptoms and biology

The seedling debarking weevil is a native insect that feeds on the bark of softwood seedlings, affecting the establishment and growth of the trees. Mortality levels on planted stock can be very high in some areas where natural regeneration is low.

The life cycle of the seedling debarking weevil takes 2 years to complete.

The adult weevils emerge from their overwintering sites in the duff-litter zone in the spring, beginning in late April. During May and lasting until July they are attracted to recently harvested sites by the scent of exposed resin, and begin to feed on the bark of softwood seedlings.

Mating occurs and the female begins to lay up to 100 eggs under the bark of softwood stumps, logs, and slash. The eggs hatch several weeks later and the larvae feed on the cambium layer (inner bark).

The weevil overwinters as a pre-pupae, or as a larva if the eggs hatched later in the season. Pupation occurs the following summer, with adults emerging from July until October. They feed for the next several weeks and as temperatures cool down, they crawl into the duff-litter zone to overwinter.

Adults feed on the bark of softwood seedlings creating irregular-shaped scars along the stem. If 50% or more of the bark is removed, the seedling will likely die. Feeding damage also creates a wound allowing disease to enter the tree.

Other information

The recommended control in Nova Scotia is to delay planting for 2 years after harvest. However, if planting must be done on recently cut sites, scraping back the duff layer or planting the seedlings in scarified sites will reduce weevil movement to the seedlings to feed by up to 50%.

Canadian Forest Service Publications

Seedling debarking weevil

Information on host(s)

All species of pine (jack, etc.); also reported on black and white spruce, fir, larch, hemlock, juniper and northern white cedar.

Main host(s)

Conifer

Date modified: