Juniper Rust

Gail Ruhl, Sr. Plant Disease Diagnostician, Purdue University

Following spring showers and warmer temperatures, the overwintering, brown, gall-like structures (Fig 1) of the fungus Gymnosporangium juniperi-virginianae (causal agent of Cedar apple rust ) growing on eastern red cedar (Juniperus virginiana) trees are bursting  forth with bright orange, gelatinous protrusions called telial horns (Figs 2,3). Spores produced from these cedar galls are dispersed by wind-blown rain to infect leaves of various apples and crabapples (Fig 4). 

During midsummer, spores produced from infected apple and crabapple leaves will be blown back to the eastern red cedars, completing the life cycle of this rust fungus. The disease generally does not cause significant injury to junipers. For more information on these diseases and their control, refer to BP-137-W

Additional infromation can be found here.