Proteoteras arizonae
Hosts: California boxelder
Damage: Close inspection reveals small larval entrance holes near the base of current growth. Small amounts of frass may adhere to webbing at entrance holes. Splitting twigs length-wise reveals larval galleries 25 to 35 mm long and virtually free of frass, except near the lower ends of the tunnels. Wilted, dying, and dead twigs may be found scattered throughout the tree crown. This borer does not cause spindle-shaped or gall-like swellings of the infested twigs as does P willingana.
Range: AZ, NM, CO, CA. Likely in UT and NV
”- James D Solomon: (1995) Guide to Insect Borers in North American Broadleaf Trees and Shrubs©