Saving Barn from Powder Post Beetles

[powderpostkiller]

Hello everyone,

I own a 30x50 barn in Nova Scotia that was built sometimes in the 1910s and is constructed mostly of hemlock.  I have owned it for 2 years and have noticed recently for the first time fresh little piles of sawdust which I have concluded are most likely from powder post beetles.  Once I realized this, I emptied the barn, gave it a wicked cleaning, got rid of all loose hay, burned all infested wood that didn't need to stay, cleaned everything within reach and sprayed it with a combination of borax and water (something I had actually read on this forum).
I now have two questions for you guys.
I noticed fresh holes this week.  Coming out of floorboards that I had just cleaned absolutely soaked with the borax mixture.  It was my understanding the beetles only came out in late spring/early summer.  Has anyone else had this experience? I haven't been able to find enough information about their habits.   I really want to learn more about their cycles so I can time my spraying every year until they're done with my barn.  The barn currently is very solid.  We had quite a few blow down with Fiona in 2022 but mine is still standing tall.

And my other question and most important right now.  I am looking to treat the lumber inside to deter them from laying more eggs.  I am thinking of a stain of sorts that would make the lumber seem less inviting. What would you guys do in this situation?  I would assume something oil based would really penetrate the wood.  I have used Lifetime wood treatment on fenceposts because of its friendliness to the natural environment.  But that's not something I want to achieve here!  I know the active ingredient is ferrous sulfate but do you think that would do anything to keep the bugs off?   I have thought about linseed oil but would they just consider that food?  I understand that linseed oil can mold but my barn is very dry inside, so dry I'm shocked the beetles want anything to do with it (they appearantly like moist environments?).

I know I can't do much now to kill the larvae in the wood but if anyone has an idea to keep them from coming back I would really appreciate some insight.  Ideally I would use something thin that I could spray like a stain.  It wouldn't have to be pretty.  I also think that a darker tone would help me identify active infestations.

I appreciate everyone's time.  Not sure what I can offer in return but gratitude.

Thanks,
The Powder Post Killer!

[Ron Scott]

You seem to have a good understanding and knowledge of the applicable controls of the Powder Post Beetle which can be persistent with a 3–7-year life span.

You should contact your local University Extension Service who may have a Staff Entomologist that can provide you with advice for applicable beetle controls and answer specific questions concerning the beetle's life span in your area and more specific to your hemlock barn situation. 

https://diypestcontrol.com/powderpostbeetles.htm

[Nebraska]

Seems like a glycol based borax solution is what you need to treat the barn wood as it penetrates dry wood better than a solubor/ water mixture.  Then maybe polyurethane after that?  Just my thoughts far from an expert and it's bits I remember from here anyway.   

[Ianab]

Was going to suggest some sort of borax solution as well. It's only really a surface treatment at this stage, but that's where the bugs lay their eggs, so it should help with the re-infestation. As you already know it won't get the grubs that are inside the wood, and they can appear several years later. I think that depends on temperature and moisture level? 

A film finish will also offer some protection. The beetle "tastes" the surface to see it it's palatable wood. If it tastes like plastic, then that's not a good spot to leave eggs. But that's probably not so practical for a whole barn.