Make sure all bark is gone and the wood is definitely dead. Put them in the dishwasher top rack, sanitize cycle with no soap. Run it a couple of times. It will stink.
You could also do a bleach/water soak in a bucket. It will lighten up the color of the wood some. After the bleach soak, rinse well, and let it soak in a bucket again with clean water and a bunch of dechlorinator to get rid of the bleach.
If you have to, you can put it in the shower as hot as the water will go, but it's not as effective as the dishwasher.