Scientific disciple of magical art - depends how you look at it really
Folk magic is more of a magical tradition than a school of scholarly research being as old as the hills, some say as old as time itself. It is as deeply ingrained to the psyche of the country folk as the changing of the seasons and has been passed down from father to son and mother to daughter for countless generations.
As they travel they notice a horrible rotten smell. As they travel it gets stronger and stronger forcing them to cover their noses and mouth less they choke on the horrible smell. Stream full of dead fish. Spawning trout die in mass quantities after they spawn littering areas with dead fish dying and deteriorating in the sun.