Killing Borer in Wooden Coasters

Question

Sorry if this question already has an answer somewhere, I couldn't find it online or within this community.

As my first foray into woodworking, I'm making relatively simple wooden coasters from red gum. The red gum has had borer in it previously, which actually lends itself quite nicely to adding interesting patterns in the coasters.

However, the obvious problem is that whether I want to keep these coasters, or sell them for a few bucks, I need to make sure any borer which may still be inside is dead.

I'd like a preferably quick way to make sure the borer inside is dead, and was wondering if there was such a method out there? The coasters are about 1cm thick, and approx 7.5cm wide.

I was thinking of just submerging them in water for eight hours, but I know some insects and larvae can survive for days, weeks, even months if they're hibernating, with little to no air, and couldn't find information on if borer fall within this category.

If there is no "quick" method, methods which take some time will also then be acceptable as an answer.

In case it's pertinent, I live in Australia. So far, the coasters have just been cut to size, but have not yet been sanded or oiled (saving those steps for after I deal with any borer).

EDIT: Accepted the answer from Chris as it (and the method in the comments for that answer) worked just fine for me. Essentially, stuck the coasters in our electric oven for a few hours, which kept the temperature around 65-70 degrees celcius over that time (measured by oven thermometer). Seems to have worked, with no discoloration of the wood, and the small cracks in the wood did not get any bigger. Note that the wood was already mostly dry - something else may have happened for green wood, but regardless, didn't in my case.

Answer 1

Best method for killing boring beetles is to use heat. Warming the wood to a set temperature for a designated length of time will eradicate the beetles and their larvae.

Beetle type determines the length of time and duration of applied heat.

• Powderpost beetles 54.4 degrees Celsius/130 degrees Fahrenheit for 2-4 hours in a kiln
• Deathwatch beetles 56 degrees Celsius/133 degrees Fahrenheit for 30 minutes

Kiln drying the wood works really well, but if you do not have access to a kiln then you could use a microwave.

Personally I have been successful with using the microwave to dry out wood rounds and buttons. 30 seconds at a time works best for me, then I can check the wood temperature and monitor for cracking/checking.

Answer 2

Borer is a little ambiguous since that describes several species of beetle. There is a basic introductory article from LifeStyle that breaks down some of those species and how you can identify which one might be in your coasters.

That would be very useful to know which species you are dealing with as it is possible you don't need to worry. You might just be looking at evidence of a previous infestation. If you are unable to figure it out on your own you could always post a picture with a ruler. Or even better I have seen species identification questions on https://biology.stackexchange.com/ so they could help as well.

Also of note: I did an answer to Protecting wood from powder post beetles which is one of the borers you might be dealing with.

Basically you are back to kiln as the best choice but since you have small objects I would choose a toaster oven over microwave since you would have better control of the temperature over time. Would function the same as the oven but would be kinder to your gas/electrical bills. Not sure of the availability in your local though.