round-headed borers, but am at a loss for information to help make this decision.

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https://duckduckgo.com/?q=round-headed+borers+arborvitae&t=ffab&ia=web

more specifically: https://duckduckgo.com/?q=round-headed+borers+arborvitae&t=ffab&ia=web

The article about wood-boring insects > primary and secondary invaders > secondary invaders atacking weakened, dying or dead trees ...

... worries me. My neighbour in the back has a dying crabapple tree that overhangs the fence into my backyard. I have already cautioned my neighbour about damage to the fence if the tree topples (the tree has been dying for maybe a decade) but now there is the additional worry of tree borers that may even become primary invaders attacking healthy trees!

Shall I start a new thread or can I piggyback on this thread?

Feel free to piggyback on this thread.

@lilnsam Thanks! I have 7 dwarf conifers within 15' of the dying crabapple tree. I can have the parts that overhang the fence pruned off (which may kill the rest of the tree) Then have the pruned tree sprayed as a preventative measure against borers spreading to my conifers, the issue is that most of the pruned tree will be on my neighbour's side of the fence, and he is not very responsive.

What is the advice of the experts here?

P.S. @lilnsam Can you try adding the 'Trees' forum to expose the issue to the experts there.

i totally understand your feelings,but we do have another option, we just repel,not kill,Sanspest,check and see,pure essential oil

I can see an essential oil being used as a preventative repellent on my dwarf conifers, provided it is effective and does not harm the plants.

I cannot see an essential oil being used as a cure if borers have already attacked the plant and hide in tunnels out of reach of essential oils.

Quick update should anyone be dealing with a similar situation and be interested. We had an independent arborist come out to assess the situation, and they actually found zero evidence of pest infestation - borers or otherwise. Sending some samples out to test for potential disease given the sections that died off.

@lilnsam You have had 3 professional opinions, 2 recommended (2 different) pesticides and 1 now looking at possible diseases.

The situation strikes me as a bit odd.

FWIW, I have a mysterious spot in my garden where I failed 4 or 5 times to grow something, I have now created some stonework there.

Yes, it is definitely a bit of a mystery. Will share update if the samples the arborist sent out provide any answers.