Thank you for contacting Ask Extension. It appears that you have Cedar Quince Rust on your Hawthorn start. This is a fungal disease that transports from one species to another. In this case, from junipers, in particular. You can spray with a fungicide that contains the active ingredient myclobutanil (Immunox, Monterey Fungi-Max or Fertilome F-Stop Lawn & Garden Spray). You will have to spray in 7-10 intervals to totally get rid of the disease. You will need to check to see if the tree is planted near a juniper, if it is, you should move it. That includes your yard and your neighbors’ yards.

To prevent this disease you will want to begin spraying in May next year. Since the tree has had this disease, it is likely that it can get it back, especially if a juniper is nearby. I have included a publication that outlines how and when to spray.

I have also included several publications for your reference:

https://hnr.k-state.edu/extension/horticulture-resource-center/common-pest-problems/documents/Hawthorns%20Rust%20Diseases.pdf

https://extension.psu.edu/hawthorn-diseases

If we can be of further assistance, please contact us again.