White Pine Weevil
Pissodes strobi (Peck)
Key Features

  • Shepherd
  • Small beetle with snout
  • C-shaped, white grubs
Browned needles on branch damaged by white pine weevil
Browned needles on branch damaged by white pine weevil
White pine weevil larvae inside twig
White pine weevil larvae inside twig
Exit holes of white pine weevil
Exit holes of white pine weevil
Symptoms

Infested trees have the leader curled into a shape that resembles a shepherd's crook. Lateral branches from the infested tree's first whorl may also be curled. The top 2 to 3 years of growth can be affected. In early summer, legless, (1/4") white, c-shaped grubs can be found in stems, beneath the bark surface or in the stem. In late summer, chip-bark cocoons are formed by larvae at the base of injured stems.

White pine weevil chip bark coccoon
White pine weevil chip bark coccoon
White pine weevil damage Photo by Vince Burkle IDNR
White pine weevil damage Photo by Vince Burkle IDNR
Biology

Adults winter in leaf litter and fly to tree tops to mate when the weather warms in the spring. Females lay many eggs in terminals that hatch into grubs that bore into shoots. Legless larvae continue to feed until July when they pupate in chip bark cocoons. Adults emerge in July and August and chew on twigs.

White pine weevil adult
White pine weevil adult
Management Recommendations

Applications of broad spectrum insecticide to tree tops should be timed to kill adults gathering on twigs in early spring (April- when forsythia bloom). A fall or early spring application of imidacloprid may also be effective in getting product into the twig when adults feed the following spring. Prune and destroy damaged leaders that contain larvae or chip bark cocoons before adults emerge in early August. Mixed species plantings of pines are less likely to build damaging numbers of this pest than pure stands of susceptible species.

Effective Pesticides

Active Ingredients include: Bifenthrin, Imidacloprid, Lambda- cyhalothrin, Permethrin, Pyrethrin

Resources

landscape report
Purdue Landscape Report
PPDL
Plant & Pest Diagnostic Laboratory