Any Ideas What This Is?

I happened to look out my dining room window this afternoon to see what looks like sawdust all over the trunk of a pine tree that's right on the line between our yard and the neighbor's garage, though there haven't been any branches cut off the tree. I went out and poked around at it a little - it didn't SMELL like sawdust and nothing seemed disturbed around it. Am I missing something obvious? It was dry and powdery, so it would have just shown up after the rain today.