juniper hawthorn rust (cedar apple rust)

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jacqui_ontario (Zone 5b) May 13, 2006

Hello,
Not sure if this is the best forum for help with juniper hawthorn rust, so if there's a better one, please let me know.

This year my Rocky Mountain junipers (Juniperus scopulorum) have developed this rust, with galls and after a heavy spring rain the orange jelly masses have appeared. The host plants are hawthorn, apple, crabapple and mountain ash - all of them common in the neighborhood. The R M junipers are exclusive to my garden! So I think removing the junipers is the best solution as I can't treat the many host plants with fungicide.

The junipers are planted in my perennial beds as a property boundary screen and would prefer to wait until the ground is frozen to cut them down. The spores will be carried off by the wind in a few days anyway. Should I consider spraying the junipers now to prevent this spread of spores and with what?

When I choose replacement evergreens, should I avoid all junipers?
Thanks for your help
Jacqui

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Penn_Pete Glen Rock, PA May 13, 2006

If it is any comfort to you, the junipers are the least affected of the plants this fungus infects. So if you don't mind the orange blobs, ignore them and leave your trees alone. The folks with the deciduous trees are the ones who will get tip dieback from the infestation, and those who plant hybrid crabapples without checking for the tolerance for rust are probably already having bare trees in July, and will continue to even if you cut your trees down.

For more complete info, you can Google Cedar-Apple-Wheat rust, or cedar-apple rust or any combination of names. You seem to worry about the neighbors' trees (good for you), but your solution seems a bit drastic. The list of common evergreens that host the rust include many native species that are common within a mile of you, so I bet that without your trees the diesese will still appear when conditions are favorable.

Post #2275474
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jacqui_ontario (Zone 5b) May 13, 2006

Thanks Pete for your advice...I'm not quite as good as you have assumed. In my garden I have an old gnarly common hawthorn that my husband loves and an apple .... the neighbors on either side have an apple, a crabapple and mountain ash that provide privacy for my garden. (Also, the last few years my serviceberry tree leaves have been affected with a little bump which yellows part of the leaf and some of the leaves drop earlier than normal. So, I'm suspicious they may have joined the host group.)

And I'm pretty sure I have the only RM junipers within a mile as I transplanted these native junipers from out in the countryside.
Jacqui

Post #2275583
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StarhillForest Illinois, IL(Zone 5b) May 14, 2006

If you live in Ontario (?) you must have J. virginiana, not J. scopulorum. But either one hosts the rust. Regardless, I agree with Pete.

Guy S.

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