HOSTS: Colorado blue spruce, Englemann spruce.
DESCRIPTION:
The
adult stage of the white pine weevil is a small (1/4 inch) snout beetle
flecked with brown and white patches. Larvae look like a grain of
cooked white rice with a brown head.
LIFE
CYCLE: The
insect overwinters in the adult stage under leaf litter and in other
protected areas. In late spring to early summer, weevils become active
and seek out spruce trees. They feed on the cambium of main branches
near the leader and insert eggs into the feeding cavities that are
formed. Eggs hatch in 1 - 2 weeks and the grubs tunnel downward
underneath the bark. Damage increases as the larva grow. Wilting of
terminal branches becomes noticeable by mid-summer. By late summer, the
top of spruce trees display a characteristic dead "shepherd’s crook".
When full grown, the larva tunnel deeper into the stem and form a
cocoon made of wood chips in which they pupate. In about 2 weeks, adult
beetles emerge leaving small holes in the bark. Adult weevils feed on
the needles, buds, and twigs of spruce for several weeks before going
into a dormant condition for overwintering.
CONTROLS:
Cultural: As soon as the ground begins to thaw in
early spring, rake up the needles from beneath spruce trees to disturb
overwintering weevils. Leave the soil exposed until spruce buds begin
to break, then mulch with 1 - 3 inches of composted wood bark chips
(such as Soil Pep). Remove and destroy wilted terminal branches as soon
as you notice them.
Botanical: Spray only the tops of trees
thoroughly with a rotenone/pyrethrin mix when spruce buds break and
begin to grow or "candle" in the spring.
