I heard this from a lady from Canada and it was fascinating . She theorized that the clear cutting of cedars (ashe juniper) opened the door to the infestation. I didn't get into hard details but this is the basics:
She talked about the root network of both trees comingling?
Maybe a physical buffer for it to reach the oak tree? Think of it like a monoculture vs poly.. if its transmitted by a beetle, the beetle can jump from tree to tree. With 100 cedars to 1 oak (gut guessing) it's harder for the beetle to find the next oak.
Then i wonder if there's something in the sap that chases off the beetle. In that case, would using cedar chips be good around open oak trees? They are very easy to obtain. I have several loads right now.
I do very little cedar cutting. Mainly just the ones choking out oak trees. Like the trunks are touching each other or are a foot away. But the area trend has always been to clear cut for pasture or aesthetics. Maybe some should stay choked (protected). I think im doing it for the oak, but am rethinking it. One that i cleared had a very nasty looking scar on the trunk that came from the cedar trunk encroaching.
I have some dead oaks and plenty of live healthy ones. Ive seen no evidence of any dieing in the 7 years i have been here. The dead ones are covered in mustang grapes. One recently looked like a giant teepee with all the grapes vines, but crashed down this past year. This tells me it has been dead a long time.
Last comment, my search here only found one thread by ludens on a cedar elm guild from 2012. She has oak wilt. I'm curious how much clearing was done, were the trees already dead. Does any of this sound plausible?
My understanding of oak wilt is that beetles that feed on oak sap will spread the disease around an area. So anything that causes oak sap to be exposed could invite the beetles. Oak trees fuse their roots together so if one oak gets it, the others nearby will get the disease through their roots. There could certainly be some trees who's roots could prevent the oaks from fusing and thus reduce the spread.
I'm surprised to hear that oak and cedar are commingling in your area. Here the oaks like it up on the dry land and the cedars are down in the low/wet land.
Here's a before and after. This a young thicket. I have the same with mature trees.
Another person, on an episode of Central Texas Gardener, stated that cedars were nursery areas for oak trees. She said that the mulch under the cedars is very tuff. That the only thing that can break through it was acorns. The squirrels do the planting.
I have not seen evidence of this though. Glancing through i think the oaks are older than the cedars.
Oh, live oak is the primary oak here. The ones with small.leaves that stay on through winter. Leaves are just now dropping.
Her main focus was on the cedar roots doing the work to keep oak wilt out. Maybe it exudes something that kills it. Not sure. I cant remember her title. Best i can describe is a permaculture natural arborist/healer of the land. Using natural things to heal trees. Her knowledge was nice. I need to get her last name. First name is vivian. She was touring this area with Zach Weiss at Elemental Ecosystems. Lets say Zach comes over and says this land is not suitable for his specialty of water retention (no clay in soil, etc), she can come in and work with species that work together for your conditions. Medicinal plants are included with knowlecge of what they do.
My comments above probably aren't applicable at all to your situation. Here we have hundreds of acres of cedars sitting in soggy soil and then up on the ridges we have hundreds of acres of maple/birch/oak/pine forest.
But I still think the main way the disease moves is beetles looking for fresh oak sap. Maybe your cedars keep away things that damage the oaks and then the beetles can't find them. Or the aroma of the cedar confuses them. I believe the only time the roots come into play is if one oak is infected and its roots are grafted onto a neighboring oak.