April 24, 2010
Cedar-apple Rust
Gymnosporangium juniperi-virginianae
These weird formations are two stages of the life cycle of a heteroecious (having two hosts) plant-pathogenic fungus which alternately infects members of the genus Juniperus (in this case Eastern Red Cedar, Juniperus virginiana), and members of the Rose family. The orange tentacle-like structures are spore producing tubes called telial horns. At Fresh Pond, the secondary host is the Juneberry or Shadbush (Amelanchier arborea.) The fungus creates dead spots on the leaves of the Shadbush, and orange Medusa-like tentacles on the fruit.