Invasive insect affects Utah native aspen trees

Nov 11, 2021

Oystershell scales cover the bark of an aspen tree in Arizona.
Credit USU Extension

The Oystershell scale is an invasive insect that can weaken and kill aspen trees has recently been confirmed in native forests in Utah. The insect has likely been affecting trees and shrubs in Utah’s landscapes for decades, but, it wasn’t until recently that the USDA Forest Service’s Forest Health Protection program has confirmed its presence in the Uinta-Wasatch-Cache National Forest in Pole Canyon, east of the Provo area.

According to Darren McAvoy, USU Extension forestry professor, the oystershell scale is a tiny sap-sucking insect that matures over the summer and develops a waxy outer shell that looks like a tiny oyster shell attached to the bark of the tree. Initially they will affect a small portion of a tree but can eventually encrust whole branches and cause branch dieback, leading to tree death.