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Western Spruce Budworm - Choristoneura occidentalis Freeman  
Jeffrey J. Witcosky, USDA Forest Service,
www.ipmimages.org
David J. Moorhead, The University of
Georgia, www.ipmimages.org
 HOSTS: Spruce, fir, Douglas-fir. DESCRIPTION:
The
larvae have olive brown to reddish brown bodies with brownish heads.
They have prominent, ivory-colored, paired spots on each body segment.
They range in size from 1 to 1-1/2 inches long at maturity. The adults
are highly variable in color from mottled med-dark brown to orange
forewings and tan hind wings, their wingspan is about 1 inch. LIFE
CYCLE: There is
one generation of budworm per year. Adult females lay a shingle-like
mass on the underside of needles. Eggs hatch in early autumn and the
newly-hatched larvae migrate to overwintering sites in silken shelters
under bark scales or among lichen. Larvae emerge in late spring to mine
buds, developing cones and old needles. As new needles emerge they are
webbed together in protective nests where the larvae feed until they
are mature in about 30 - 40 days. Pupae are formed in the silken nests
and adults emerge in late summer to mate and lay eggs. CONTROLS:Biological: Birds are important predators. Spray Bacillus thuringiensis (Bt-kurstaki) plus 1 - 2 Tbsp. insecticidal soap per gallon of water at first swelling of spring buds. Repeat applications necessary. See Bacillus thuringiensis. Botanical: Spinosad or neem(Bioneem, Azatin, Neemix, or Nemagad) plus insecticidal soap when buds swell on spruce trees. |
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