Cedar-Apple rust treatment for Hawthorns addendum - Ask Extension
I just wanted to add a couple pictures to my prior email for your diagnosis/assessment purposes.
Knowledgebase
Cedar-Apple rust treatment for Hawthorns addendum #803905
Asked July 31, 2022, 5:27 PM EDT
I just wanted to add a couple pictures to my prior email for your diagnosis/assessment purposes.
Benton County Oregon
Expert Response
(FYI - Just moving this information over from the previous question # 0073835 which I will now close.)
Greetings, I’ve been researching foliar spraying to control
gymnosporangium fungus (cedar-apple rust). The timing is the issue: if I
spray our trees, which are in a wetland area, before budbreak in Spring
I am struggling with the research suggesting it kills not only aquatic
invertebrates but (if I wait until leaves are out with blossoms)it is
banned in the EU due to it’s likely roll in the great bee decline.
We have already lost 1/3 of the 15 or so wild hawthorns in that area and
we’d like to save the others. We are even considering removing and
burning the western red cedars in that area because them seem to have
been the original hosts (with orange gelatinous telia growths 2 winters
ago).
I would love to know if there is another fungicide that could help as a
DRENCH soil treatment in June—I’m dreaming, right because the fungus is
only in spore form at that time?—but haven’t been able to find one.
Any suggestions would be appreciated. Thanks, Aaron Rousseau in North
Albany, Oregon, <personal data hidden>
Greetings, I’ve been researching foliar spraying to control
gymnosporangium fungus (cedar-apple rust). The timing is the issue: if I
spray our trees, which are in a wetland area, before budbreak in Spring
I am struggling with the research suggesting it kills not only aquatic
invertebrates but (if I wait until leaves are out with blossoms)it is
banned in the EU due to it’s likely roll in the great bee decline.
We have already lost 1/3 of the 15 or so wild hawthorns in that area and
we’d like to save the others. We are even considering removing and
burning the western red cedars in that area because them seem to have
been the original hosts (with orange gelatinous telia growths 2 winters
ago).
I would love to know if there is another fungicide that could help as a
DRENCH soil treatment in June—I’m dreaming, right because the fungus is
only in spore form at that time?—but haven’t been able to find one.
Any suggestions would be appreciated. Thanks, Aaron Rousseau in North
Albany, Oregon, <personal data hidden>
The images show us necrotic spots on leaves. Leaves seem to turn yellow and fall off the tree. Another images shows extensive defoliation of some trees. The spots on the leaves in your images are not rust. These look more like scab spots and an outside change they might be something called leaf spot. Apple scab has been very common this spring and the most likely diagnosis of your images. To confirm you would not see the same spot on both sides of the leaf. Have a look here for chemicals to choose from if you want to spay:
https://pnwhandbooks.org/plantdisease/host-disease/hawthorn-crataegus-spp-scab
The other leaf spotting fungus common here is different and can be diagnosed if you have the same spot on the top, turn leaf over and have the same spot showing through on the bottom of the leaf. Here is some information on that disease:
https://pnwhandbooks.org/plantdisease/host-disease/hawthorn-crataegus-spp-leaf-spot
You might consider having a landscape company involved to help make the applications and/or select chemicals. In the long run, there is no need as these trees will survive quite well on their own. It has just been an unusually wet spring.
https://pnwhandbooks.org/plantdisease/host-disease/hawthorn-crataegus-spp-scab
The other leaf spotting fungus common here is different and can be diagnosed if you have the same spot on the top, turn leaf over and have the same spot showing through on the bottom of the leaf. Here is some information on that disease:
https://pnwhandbooks.org/plantdisease/host-disease/hawthorn-crataegus-spp-leaf-spot
You might consider having a landscape company involved to help make the applications and/or select chemicals. In the long run, there is no need as these trees will survive quite well on their own. It has just been an unusually wet spring.
