Cedar-hawthorn rust on fruit of cockspur hawthorn (Crataegus crus-galli)
Cedar-hawthorn rust on the fruit of cockspur hawthorn (Crataegus crus-galli)
Cedar-hawthorn rust on hawthorn (Crataegus)
Cedar-hawthorne rust on fruit of running serviceberry (Amelanchier stolonifera); note aecia (cluster-cups) on fruit
Orange telial horns of cedar-hawthorne rust gall on juniper (Juniperus)
Overview
Cedar-hawthorn rust (Gymnosporangium globosum) is a closely related rust disease of cedar-apple rust (G. juniperi-virginianae), and cedar-quince rust (G. clavipes) that require two hosts to complete their lifecycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Cedar-hawthorn rust, in addition to affecting many hawthorns, apples and crabapples, can sometimes infect pears, quince and serviceberry.
Symptoms and Diagnosis
Life Cycle
The disease overwinters as galls on infected junipers. During wet spring weather, "horns" extrude from the galls and produce spores. These spores are then windblown or carried by insects to the leaves of nearby susceptible hawthorn plants. The spores then turn brown, infect the leaf tissue, and form yellow spots on the leaves. In the late summer, spores are produced on hawthorn leaves. They are windblown back to needle bases or cracks in juniper twigs. After infection of the juniper, small galls form, thus completing the cycle. It takes two years to produce a spore-bearing gall.
Integrated Pest Management Strategies
1. For both hawthorns and junipers, prune out diseased branches. The spread of cedar-hawthorn rust can be limited by reducing infested plant parts.
2. Live with the disease. The disease rarely kills trees. It can, however, disfigure plants when twigs are infected.
3. Use fungicidal sprays. Both junipers and hawthorns can be protected from infection with fungicide applications during periods of spore production. Pesticides registered for use include chlorothalonil and mancozeb. Spray hawthorns prior to spring bloom with a fungicide. Thorough uniform coverage of plant surfaces is essential for good disease control.
4. Avoid planting susceptible hawthorns within a two-mile radius of junipers. This may be impractical in an urban environment.
5. Replace infected trees with resistant hawthorn varieties.
Organic Strategies
Strategies 1, 2, 4, and 5 are strictly organic approaches.
Pesticide Disclaimer:
Always follow the product's label and ensure the product is effective against cedar-hawthorn rust. Not following the pesticide label before usage is a violation of federal law.
Updated 8/2025