Hawthorn rust is caused by the fungus Gymnosporangium globosum.
Signs and Symptoms
The rust fungus causes small yellow spots on hawthorn leaves. These spots eventually enlarge and often have a reddish border. The centers of these yellow spots later show small black spots. On the lower leaf surface, directly above the spots, small brownish tube-shaped structures form. Infected leaves may eventually yellow and drop prematurely from the tree.
This disease is also referred to as cedar-hawthorn rust because the fungus requires two hosts to complete its life cycle.
The cedar-hawthorn rust fungus
Type of Sample Needed for Diagnosis and Confirmation
Collect 3 to 5 twigs and fruits. For further information go to sample collection
If desired, fungicides can be used to protect hawthorn leaves from infection. Labeled products
See this article for more information about cedar rusts.