So far I've found this on the internet while searching for information about it.
Found on Yahoo! Answers.
By far the BEST method to sterilize ANY wooden branch (assuming that you mean one that you have collected from outside) is to place into a warm oven . . . Your cooker.
SOAK the branch/branches firstly in your bath using nothing else except for very hot (not boiling) water. Any insects etc. This will be enough to destroy any noticeable insects. Then it is just simply a case of placing the said branches in a hot oven for an hour or so to destroy anything else which is not visible to the naked eye.
This method is tried and tested and of course requires no chemicals or other harmful toxins whilst rendering your wooden branches completely devoid of hazardous infections.
I've been washing natural limbs and branches, giving them a light once-over with a small scrub brush and then letting the excess water dry off.
After a drip-dry, I lay it in the oven and set to "preheat" at 300oF. When the preheat light goes out, I turn off the oven, open the door and and leave it in. I remove it when I can handle it with bare hands.
One must be very careful heating wet rocks beyond the boiling point and it's not recommended. If one feels compelled to sterilize this way, temps should be brought up gradually to allow the water vapor to escape before dangerous internal pressures can occur.
It is well known among campers that laying a wet rock in or along the fire perimeter can cause an explosion due to steam pressure.