Juniper Webworm
Contact: Eric Day, Manager, Insect Identification Laboratory
August 1996
Juniper Webworm
1989
Lepidoptera: Gelechiidae, Dichomeris marginella
Plants Attacked
Red cedar, Irish juniper, also-pfitzer, hetzi,
and creeping juniper.
Description of Damage
Large brown patches scattered throughout
the plant are apparent from a distance. Close examination shows
masses of brown needles webbed together and pulled in toward the
twigs. When pulled apart, larvae can be found within the webbing
and dead needles.
Identification
Larvae are about 1/2" long when fully developed.
They are brown with longitudinal reddish brown stripes. The
adults are not often seen, but are light brown and almost 1/2"
long.
Life History
Where one generation occurs, moths occur during
late June and July, when there are two, adults may occur in May
and June and again in July and early August. Eggs are laid on
the foliage and hatch shortly afterward. Larvae feed for a few
to several weeks, pupating in the webs. The winter is spent as
young larvae in the webs. It is likely that one generation
occurs in Virginia. Most larval development occurs in the
spring and early summer, but youngest larvae are present in late
July and August until the following spring.
Control
Insecticides can be applied in the spring, but the best
time is in late July or early august. Sprays are most effective
against young larvae in late July and August, but can be applied
in April and early May. Strong spray streams should be directed
into the webbing to provide maximum penetration.
Remarks
This pest has not been reported as common in the state,
but does occur throughout Virginia. If heavy populations build
up, it can be a serious pest. Apply control measures when
evidence of infestation is first noted.
