Cedar-apple rust is a fungus disease of apple and cedar and spends parts of its life cycle on each host. It is caused by Gymnosporangium juniperi-virginianae. The fungus can infect leaves and fruit of most cultivars in the eastern region. This table lists juniper, hawthorn, and crab apple cultivars with resistance to rust diseases.
| Juniperus (Juniper) | Crataegus (Hawthorn) | Malus (Crab Apple) |
|---|---|---|
| Cedar-apple and hawthorn rust resistant | Cedar hawthorn rust resistant | Cedar hawthorn rust resistant |
| J. ashei | C. crus-galli | ‘Adams’ |