External evidence consists of pitch tubes at the point of
entry on the cone stalk or the base of the cone. Following attack,
cones turn brown and wither. If beetles have emerged, small round
exit holes may be found on the outside of affected cones. Inside,
beetles leave cones riddled with tunnels and frass. Adult beetles
are reddish brown to black, shiny bark beetles. Larvae are small
white, legless grubs.
Biology: One generation is produced per
year. Adult beetles bore into the base or stem of immature second-year
cones in the spring. A gallery is created along the cone
axis, with eggs deposited along its sides. The creation of the gallery
severs the conductive tissues of the cone, killing it. Larvae hatch
and feed on the scales, seeds, and tissues of the cone. The brood
complete development during the summer within the cone, and usually
overwinter there. Some new adults emerge and may bore into shoots
or conelets and overwinter.
beetles cause the death of second-year cones. The amount of mortality
is highly variable but in some years a large proportion of cones
may be attacked.
Similar Insects and Diseases: This insect
is best distinguished from other insects that attack developing
cones by the presence of the pitch tube on the cone base or stem.