More powderpost beetle questions

[Tom Porter]

A few weeks ago, I discovered what I believe are powderpost beetle signs in some live-edge black walnut I have. I wanted to make a few cutting boards and serving trays out of some of it. After some advice from Scott Smith, I built a small simple kiln, which after some trial and error, I can get to 150F, so I should be able to sterilize the wood. But this begs the question: would the wood be safe for food contact after it is sterilized? I mean, the bugs will be dead but just because they aren't alive doesn't necessarily mean the wood is safe. I may be overthinking this but I'd like some feedback from anyone with experience or knowledge on the subject.

[Peter Christensen]

You ever see a sick woodpecker? Go ahead and don't worry about the dead bugs. Recognize that the holes the bug leaves behind can hold food that can be a breeding ground for bacteria but so can open grained wood. I'd be more worried about bugs in the untreated wood getting into the shop or building it is stored in.

[Danny Hamsley]

If you have sterilized the wood for 24 hours at 150 degrees, you should be fine. PPB's usually only infest the sapwood in walnut, so if you want to be doubly safe, trim off the sapwood. However, I would not hesitate to use it as is.

[Tom Porter]

24 hours at 150F? I was under the impression that a relatively short time at which the wood internal temperature is 133F was sufficient. Of course, it takes the wood some time to reach that (thickness being a factor). Thus, the 4 hours at 150F I had read. I was going to aim for 6 to be sure. I suppose I could do 24 hours as long as no one tells my wife there’s a space heater in the garage running all night.

[Danny Hamsley]

You have to reach 133 degrees internal temp in the wood. To assure that you get to 133 degrees inside the middle of the wood, you have to have a higher surface or air temperature. That is the reason for 150 degrees for 24 hours. Gives time for the heat to penetrate into all the pores of the wood all the way to the center to assure that there is enough time at 133 degrees internal temp to kill any beetles, larvae, and eggs.

[Scott T Smith]

Somewhere I have a chart that lists time to reach sterilization temps based upon Lumber thickness and chamber temp, but it’s not accessible to me right now.

if I’m finishing a kiln run and the wood is already at 120, then an 8 hour sterilization cycle at 150 is adequate to reach 133 throughout for 8/4 and thinner Lumber.

However, if I’m bringing the Lumber up from room temp, then as Danny advises 24 hours would be the minimum.

[Tom Porter]

Thanks for the advice. I heated the wood for 30 hours, with the probe thermometer reading between 150 and 180 as I periodically checked it. The wood was about 5/4 for the most part. If the bugs survived that, they can have it.

[roger wiegand]

As far as I know, powderpost beetles, like most insects, are perfectly edible, and probably a reasonably good protein source. Insects were a primary source of nutrition for humans over the last several hundred thousand years, still are in much of the world. (And they are probably coming to a Whole Foods near you. )

[peter Joseph]

Interesting approach for sure and it certainly sounds like you got the job done. Why not just spray Timbor though? I'm guessing bc of the food application?

[John K Jordan]

Interesting approach for sure and it certainly sounds like you got the job done. Why not just spray Timbor though? I'm guessing bc of the food application?

By "interesting approach" do you mean the heating process? I understand Timbor sprayed on the wood surface will help prevent bugs from entering wood but the heat is necessary to kill bugs already in the wood. Maybe Timbor on the surface will kill them when they finally eat their way out a year or two later.

BTW, I was once incredibly lucky to witness a PPB actually eating its way out of the endgrain of a walnut turning blank. Some time later I witnessed a flock of PPBs flying toward, landing on, and beginning to chew their way into some maple I was cutting outdoors, obviously attracted by the smell. My life is now complete.

JKJ

[Scott T Smith]

Interesting approach for sure and it certainly sounds like you got the job done. Why not just spray Timbor though? I'm guessing bc of the food application?

Timbor won't penetrate all of the way through the lumber, as Roger mentioned. Additionally it is never a good practice to rewet dry wood (and by applying Timbor you would really need to saturate the lumber in order to gain even a small amount of penetration).

Timbor is best used on green lumber; Boracare is best used on dry lumber.

[Tom Porter]

As suggested, my concern about a chemical treatment was based on the food contact of the final product.

I finished some of the pieces. A few look great. On two of them, the insect damage is more prominent than I anticipated. The finish (mineral oil with paraffin wax) brought the damage out a little bit visually. I'm not sure how I feel about the look...