Crabapples (Malus spp.) are susceptible to several diseases, most prominently apple scab, fire blight, powdery mildew, and cedar apple rust.  The International Ornamental Crabapple Society, a network of public gardens with extensive crabapple collections, assesses these flowering trees annually for disease resistance as well as aesthetic qualities.

Disease resistance varies in different parts of the country. For example, a cultivar that succeeds in the northeast, where apple scab is the most common disease, may not thrive in the south, where fire blight is a more pressing issue.

Here is a partial list of crabapple cultivars that have proved resistant to apple scab, fire blight, and powdery mildew in the Northeast:

• Malus 'Louisa'
• Malus 'Molten lava'
• Malus 'Adirondack'
• Malus 'Prairifire'
• Malus 'Ormiston Roy'
• Malus 'Schmidtcutleaf' Golden Raindrops®
• Malus 'Sargentii'
• Malus hupehensis (tea crabapple)

Because of regional differences in disease resistance, consult Cornell Cooperative Extension, University of Connecticut, Rutgers  or your local agricultural cooperative extension for information specific to your area.

Cedar apple rust is a fungal disease which needs two hosts: apple or crabapple trees, and eastern red cedar (Juniperus virginiana) or other junipers. Orange-colored galls overwinter on the junipers and in spring produce spores which are air-carried to apple and crabapple trees. Leaves of infected trees develop bright orange or yellow spots; eventually the trees may become severely defoliated.  Fruit can also be infected.

To control cedar apple rust, junipers must be removed from the vicinity of the crabapples, and fungicides used if necessary. Crabapple cultivars less susceptible to cedar apple rust include:

• Malus 'Ellwangeriana'
• Malus 'Henry Kohankie'
• Malus 'Ormiston Roy'
• Malus 'Red Barron'

For more detailed information on cedar apple rust, visit Cornell's plant clinic and cooperative extension pages.

For tips on a variety of gardening topics, see our Plant Information Guides.

- Courtesy of NYBG Plant Information Service