On native giant reed. Tentative ID. People I've talked to in the MN DNR who are Invasive Species Specialists report that this fungus doesn't affect the non-native population here in the state
Elm/Ulmus
I believe this is fungal in origin with spore capsules at the termini. The strands are about 2 inches (5 cm) in length. Growing from (possibly) bird droppings in an outdoor flower pot.