Cedar-apple rust is a fungal disease that requires two different hosts - first a cedar and second a member of the rose family - to complete the life cycle of the fungus Gymnosporangium juniperi-virginianae.
The photographs here show the orange gelantized telia on an eastern red cedar tree in spring. Basidiospores released from these telia can only infect members of the rose family - Rosaceae - first causing yellow lesions on the leaves and later maturing into orange pustules.
For more detailed information on cedar-apple rust and its life cycle visit the Missouri Botanical Garden cedar-apple rust page.
For a taxonomic tree and links to other fungi posted on Wild Florida Photo see the Fungi at Wild Florida Photo page.