I have a Oxo Good Grips wooden spoon that I bought about six months ago. For the past couple of weeks, I have noticed that each time I wash it (by hand), that there is a mysterious, green spot that keeps coming back. I've tried scrubbing it off and it will go away temporarily, but returns as the spoon dries. It appears to go down into the wood.

Anyone else ever have this happen? What is it, and how do I make it go away?