Oystershell scale is a hard-shelled immobile scale insect with a shape very similar to its namesake: oyster shells. Commonly found on aspens, cottonwoods, lilacs, and other thin-barked deciduous trees, oystershell scale can severely weaken its hosts, eventually draining them completely. Infestations are often overlooked until branches begin dying back.
PHOTO (left) accredited to: W.M. Ciesla, FHMI, www.Bugwood.org
PHOTO (middle) accredited to: Emily Jack-Scott
PHOTO (right) accredited to: W. Cranshaw, CSU, www.Bugwood.org