I noticed these bizarre, curled leaf galls on Poison Ivy (Toxicodendron radicans) recently, but I was unable to stop to inspect them more closely. I did not initially see any signs that these structures were fungal in nature (very hard to get a good view when one has a curious 100+lb dog in tow), but my return to this location now has me questioning this entirely. The one thing that really struck me was that these galls were near or on plants infected Poison Ivy Rust Fungus (Pileolaria brevipes). I saw signs of infection on both leaf surfaces and petioles.
I bisected these gall-like structures as best as I could whilst wearing nitrile gloves (urushiol will permeate latex and some other materials), but none of the interiors revealed any arthropod inhabitants. What I did notice was that the interiors of the galls were of a similar rust/pink hue as the stem infections by P. brevipes.
Bisected gall
I'm far from an expert on the life cycles of Uredinomycete fungi, but from what I'm reading, many of them have five spore stages with two required hosts (heteroecious). P. brevipes seems to only require one host (autoecious), Toxicodendron radicans, while having three spore stages.
Itβs a really wild thought, but are these galls just a part of that spore stage?
Location: Etowah County, Alabama, US
Date Observed: April 25, 2023
Habitat: mostly coniferous forest edge
Pileolaria brevipes on the petiole of Toxicodendron radicans
Pileolaria brevipes on the leaves of Toxicodendron radicans
