The literature says that the beetles dig straight in and then turn and make one or more "galleries" off the main hole.  So if you can poke at them before they've made the turn, you might be able to get them.  (That was the case for me).  Plus, if you get some of the sawdust out, hopefully some of the insecticide will reach to them.
I just got back from camping along the Delaware River between New York state and Pennsylvania.  The very first bug I saw was an Ambrosia Beetle!  There are signs around warning the campers not to bring their own firewood because it has become a known method of transporting the beetles from hundreds of miles away.  If you do bring your own wood, they warn/plead for you to burn it all and not leave any.
I was at a cookout a few miles from my house.  The owner (not a fig grower or a grower of fruit trees of any kind) was complaining about the gnats buzzing around.  They were ambrosia beetles.  They got worse once a few bottles of beer and other alcoholic beverages were opened up -- since they're attracted to the alcohol in them.
Oy!
Jim

I could just cry!!!  The horrid little creatures!

You may not want to use this on edibles, but 2 years ago I had a boring type thing attack a beautiful tree I have on the side of my house.  Unfortunately I haven't had it ID'd yet.  Anyway, I used Bayer tree and shrub  that is poured around the base of a small tree and at the drip line of a large tree.  It worked like a charm on that tree that is about 30' or so from my in-ground fig and garden.  I prefer organic methods, but sometimes there isn't time for that.

Good luck getting rid of those horrid little creatures!

Does anyone know more about these things, beyond the limited info on wikipedia?  Are they invasive/introduced, or do they naturally live here?  If the latter, then we can assume that there was some set of circumstances over the last few months or year that led to this apparent population explosion.  Also, we can hope that whatever naturally preys on them will start to multiply and take down their numbers.  Might take a season for this to happen though. 

There is a huge old fig tree across the street that seems to have died almost to the ground and has these holes all over it.  So I know they are around me as well.  However, I have about 100 potted fig trees, and they are all healthy with no signs of these beetles.  So I'm wondering why they were spared (so far)?  Is it because they were in the garage during the initial wave of these beetles?  I moved them out around the end of April.  Is it something else specific to growing in pots? 

Good questions Rob

My Celeste with the beetle infestation is in ground since last Summer. Made it through the extreme winter temps but the beetles found it. Maybe the cold frozen area was an open invitation for them to make that branch their home. My potted fig trees that were stored inside, all look good. Right now I'm going to trim a large dead looking branch off my inground HC, it looks like a good place for a beetle attack.

Here's a snap of my larger in-ground HC with one branch (poking up and out, right side) that appeared dead compared with the rest of tree. With beetles so close by I didnt want to provide them with any more interesting bed town locations. So, I just pruned it. Surprisingly, although it looked like dead wood, the pith inside appeared green, just no growth. This was one branch that I didn't have as well covered as rest of tree this Winter.

I just spoke with the Maryland Dept of Agriculture. The inspector was very concerned and extremely knowledgeable. The good news is, this beetle that has bored into my fig trees is called Ambrosia Beetle and is common to our area, not to be confused with the Long Horn Asian Beetle, which is a threat. The difference is, the Ambrosia Beetle will leave pin holes in the wood whereas the Long Horn will leave dime sized holes. He went on to say the Ambrosia Beetles attack stressed, weak, or dying trees. Given the past winter was so hard on the figs this all makes sense. I have cut the fig trees down to the ground, there are already foot high shoots coming up off the stumps (as my trees were multi trunked) so I have a good feeling that these trees will come back. I don't think there is anything that could have been done differently given the factors that led to this. Cheers to all and may your figs come back with a vengeance! I'll keep you updated on the progress.

Here is an informative link describing the Ambrosia Beetle in more detail. What I came away with is that healthy trees are less susceptible.
https://extension.umd.edu/sites/default/files/_docs/programs/ipmnet/GAB%20Bulletin-UMD.pdf

Mark,

Looks like you are fairly close to me geographically.  Did you protect your HC?  It's great it survived so well since so many other figs go knocked to the ground over the winter.  How long has it been in ground?

The trees were not protected, and have been in the ground for 7 yrs. they are planted on the south side approx 5 feet from the house. In a way they are wind protected due to their location but not wrapped or anything.

Way to go...love the flame thrower!