Mr. Morris: I need more information. The decayed and tunneled wood pieces are what? Old root pieces as the tree seems to be somewhat surface rooted or from limbs that have fallen from the tree? In general, many of boring beetle infestations are started when a tree or part of a tree is already weakened and cannot ward off the insects. This could be could injury, heat injury, damaged root systems, etc. In other words, they are often not the cause the initial damage but opportunistic insects that thrive on weakened trees. Tell me more about the condition of the tree including how long you have been watching it. Chip Bubl OSU Extension/Columbia County   <personal data hidden>   <personal data hidden>

Thanks - your summary and picture help. The tree clearly has the robust root system that mulberries are famous for. My instinct says that the roots in question were somewhat injured either by the tripping over prior to coverage and/or greater exposure to extreme winter cold. I don't think covering them with dirt as you described would have, by itself, caused injury. But if their exterior covering was compromised, it becomes a magnet for both fungi and insects to invade and feed on the inner tissue. The initial pictures seem to indicate fairly extensive decay along with borer tunneling and frass (insect poop).

There is a root disease called Armillaria that does attack mulberries and is impossible to treat. It is fairly common on oaks but has a fairly wide host range: https://pnwhandbooks.org/plantdisease/host-disease/oak-quercus-spp-armillaria-root-rot . The mushrooms it produces are good indicators and I suspect you didn't see them. So that may not be a concern now.

But it is impossible to know the extent of damage from the damaged root pieces all the way back to where the root joins the base of the main trunk without a lot of invasive soil removal. There do seem to be other really strong roots from their size in the picture. The big risk is if a tree that big fell, it could damage a house or other structures. That is a risk you would need to assess, often with only modest actual knowledge about the root system. If there is an arborist near you, it might be worth a consultation. Hope this helps. Chip

Jim: I would let the arborist make the decision re how far back to trim the decayed roots. Plants sometimes can seal off portions of roots that are decaying from the non-decayed other portion of the live root. That sealed point is important to keep. Mulberries may be complicated that way. Chip