Host: White fir
Symptoms/Signs: Larvae mine the needles, resulting in bleached-yellow mined needles
from late spring to early fall. Mature larvae are about 8 mm long, yellowish-green
to cream colored, with brown to black heads. Pupae are orange to dark
brown, about 5.5 mm in length, and can often be seen protruding from the
hole in the mined needle prior to emergence. The adults are 11 mm dusty
gray moths. They can be seen swarming around host trees in late June and
Biology: The white fir needleminer has one generation
per year in New Mexico and Arizona. Eggs are deposited, usually one egg
per needle, in late June and July. Eggs hatch in August and September.
Young larvae immediately bore into the needle where they overwinter. As
weather warms in the spring, feeding begins. Each larva mines several
(five to seven) 1-year-old needles. Two- and three-year-old needles are
also mined during outbreak conditions. Two to six needles are usually
webbed together and remain on the tree for the duration of the summer.
Pupation occurs within the last mined needle in June or early July. Adult
moths emerge in 10 to 14 days after pupation. Mating occurs within 2 to
3 days of emergence.
After several consecutive years of heavy defoliation a high proportion
of limb mortality and widespread tree mortality may occur. This can give
individual trees or even entire stands a silvery appearance. These heavily
defoliated stands decline in vigor and may be predisposed to attack by
fir engraver beetle.
Similar Insects and Diseases: Similar defoliation
may be caused by western spruce budworm
or Douglas-fir tussock moth; however,
the larvae of white fir needleminer only mine the needles.