Which type of footwear has the highest risk of transferring didymo?

Felt-soled boots are known to pose the highest risk of transferring didymo, also known as "rock snot," due to their unique construction. The felt material can harbor microscopic didymo cells and other aquatic invasive species in its fibers. This ability to trap and retain biological material makes felt-soled footwear particularly problematic, as they can inadvertently carry these organisms from one water body to another, promoting their spread.

In contrast, rubber boots, water shoes, and canvas shoes generally have smoother surfaces that do not capture aquatic organisms effectively. Rubber, being non-porous, allows for easier rinsing and cleaning, which can reduce the likelihood of transferring unwanted organisms. Water shoes and canvas shoes, while less suited for challenging water conditions, also do not have the same porous texture that felt-soled boots possess, making them less likely to trap didymo cells.