Where is the rope stored, and how long has it been there? If it is brand new I would return it, it's just not worth risking. If it were pants or something I would just throw them in the wash- but a rope. . no way. Looking at the picture it looks like mold (or chalk, but I kind of ruled that out), I worked in a shop that kept gear in an old damp basement for ages if inventory wasn't moving. In some cases packaging or product would end up destroyed or defective.