Gymnosporangium's a genus of heteroecious plant-pathogenic fungi which alternately infect members of the family Cupressaceae, primarily species in the genus Juniperus (junipers), and members of the family Rosaceae in the subfamily Maloideae (apples, pears, quinces, shadbush, hawthorns, rowans and their relatives). In junipers (the primary hosts) (see photo), the fungus forms a ball about 2-4 cm in diameter which produces a set of orange tentacle-like spore tubes called telial horns. These horns… (More on Gymnosporangium)