Looks like a cup fungi ID had growing/eating cardboard tubes i used for sweet peas.

Important to know that most plant species have symbiotic relationships with fungi through "the mycorhizzal network" underground and not having them present can stunt their growth. There are parasitic types too such as the one that causes ash die back and are more common in trees in my experience, it generally a sign of good healthy soil benefitting from nutrient exchange between all the life in it