Yew eating insects have appeared (update) and they eat heartwood aswell.

[Strichev]

I have some highly treasured yew that's been seasoning for around two years now. It's in the rafters with plenty of airflow. Things seemed all nice and dandy until yesterday when I, to my horror as you may imagine, discovered that some exposed sapwood and also some bark has tiny holes about 1 mm in diameter in it. Not many, only about 4 per stave but problematic nonetheless.

I removed the bark from all the staves and thinned the sapwood around a hole near the edge of one of the staves to reveal the extent of the damage. Luckily it would appear the holes are "only" around 3 mm deep and could be described as chambers of sorts. Inside these chambers or holes there seems to be a tiny amount of black-ish dry matter that I hope is what remains of the larva that got taken care of by the toxins. I understand that the holes are usually exit holes but I don't think the beetle (or whatever caused this) could develop by feeding on such a limited amount of wood.

The other option I see is that these holes are chambers dug out by adult insects and that the black-brown dry matter are in fact eggs and that the sapwood is about to become a toxin tolerant, wood-munching beetle-spawning larvae bonanza. This seems somewhat unlikely as there are no further tunnels in the wood leading from these holes. Or so I hope.

Does anyone have experience with this? Would spraying a borax solution permanently prevent further infestation? I plan to fill the existing holes that can't really be dug out quickly (got to chase a ring on yew) with permethrin and then spray all my wood with borax afterwards.

[Del the cat]

Yeah, about 6 years ago someone kindly sent me some Oregon Yew billets, the sap wood was full of bug holes despite the books saying that bugs don't eat Yew 'cos it's toxic... the bugs can't read!
I did try to make one bow from two that look ed clean, but it broke as I neared full draw... yup, a bug hole right across the back just beneath the surface.
I ran the other billets through the bandsaw to cut off the sap wood. and backed 'em.
One was backed with yew sapwood from English Yew that had V thick sapwood (I christened it "Transatlantic" )
Another pair I backed with boo.
Del

[Strichev]

I was confident that the yew will be fine since it's so often written how toxic and resistant it is. You're right, sadly the bugs can't read.

I've read the thread about those billets... some really, really funny jokes about Yugoslavian yew borers there; guess what, there still is a constitution of the Socialist Federative Republic of Yugoslavia somewhere in the attic. I suppose if I throw out that booklet and everything with a red star on it, the yew eating bugs might also go away.

Since the sapwood is rather thick I'll try to reduce it enough to show any hidden holes or at least get rid of them. I really don't want to rip it off as the staves have some really nice character.

[wizardgoat]

Bugs won’t eat yew heartwood. They’ll eat the sapwood.
I’m lucky to live in an area that doesn’t really have that problem, by any chance
was the yew cut in the spring or summer?
If it were me I’d ditch the sapwood completely

[Strichev]

Actually it was probably damaged in a logging operation in late spring and had been lying there for a few days/weeks before I found it, hard to tell.

Edit: Just found a hole that goes through the sapwood and into the heartwood.

[Hawkdancer]

That news is about as cheerful as a sharp stick in the eye, or a heart attack!  There are only about 5 million types of "bugs" out there, as well as those who have developed immunity to pesticides!  Back to Joe soap and water! 
Hawkdancer

[Ryan Jacob]

Jeez what kinds of bugs do you guys have there?

[Strichev]

Maybe we have edible yew? (not gonna try it though)