Oystershell Scale
Contact: Eric Day, Manager, Insect Identification Laboratory
August 1996
Oystershell Scale
Homoptera: Diaspididae, Lepidosaphes ulmi (Linnaeus)
Plants Attacked
Dogwood, elm, hickory, poplar, apple, etc.
Description of Damage
Bark become cracked and scaly, trees
loose vigor, foliage is dwarfed and spotted with yellow. In
severe infestations may kill plant.
Identification
Scale cover resembles small oyster shell. The
adults are usually clustered together and in severe infestations
may cover the bark of infested branches completely.
Life History
Eggs laid in late fall, 40-150 per female.
Hatching occurs in late spring. Crawlers move around 1-2 hours
to 1-2 days before settling. The scales are white in color at
first but become brown with maturity. They mature about the
middle of July, mate, and lay eggs. This second generation
develops and by late fall they lay the eggs which overwinter for
the spring generation.
Control
Sprays should be applied at time of crawler hatch and
emergence from the old females, in mid-late May and again in late
July or early August.
Remarks
Populations tend to congregate on one or a few
branches or on entire tree, seldom a few scales scattered over
the host.