Hawthorn in trouble

Calgary, AB(Zone 3a)

Anyone know what this is? It appeared on a few berries & leaves. I'm going to take a ladder out & hand pick off all that I see. Should I spray with anything?

Thumbnail by joannabanana
Dublin, CA(Zone 9a)

I would guess it's one of the Gymnosporangium species, this is an interesting group of fungi that alternate between a Juniperus species and something in Rosaceae (most frequently apple, hawthorn, or quince). Often called cedar-apple rust, juniper-apple rust, cedar-hawthorn rust, etc. Unfortunately if you have a susceptible plant and you have junipers in the area, there's really not a good way to prevent it, short of getting rid of one of the hosts (if it doesn't have them both, its life cycle is interrupted and it won't cause problems). Of course if the juniper half of the problem is in your neighbor's yard then you don't have too many options! Here's an article with more info http://www.urbanext.uiuc.edu/focus/cedarhawthornrust.html

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