Hello, Within the last two months this creeping crud has appeared several times next to my front door. It grows very quickly. Also it is very crusty and crumbles when I wipe it off. Last week, I also found it growing in my garage. It seems strange how it grows straight up in a thin somewhat twisting line. It doesn't look like any pictures of mold that I have ever seen but I can't imagine what else it would be. Thanks, in advance, for any knowledge you might be able to share.