Knowledgebase

Cedar Apple Rust #831668

Asked May 23, 2023, 4:44 PM EDT

I have a row of 6 junipers planted for privacy in full sun. They have done well in this spot and have grown to over 10 ft. This is the first year that I have noticed they do not look very healthy. I noticed this past weekend when it rained they formed these orange blobs on the branches. They were covered in them and there was no way I could remove them by cutting without disfiguring the trees, and at that point I might as well just chop them down. I would like to save the trees and keep them from being disfigured. I took a picture and showed it to a local nursery. They indicated that it was Cedar-Apple Rust. They recommended a fungicide but I'm not sure that it's the correct one for this specific fungus. Is there any treatment I can try that would help treat the fungus and keep it from coming back? Please provide specific information on what to use, what months to use it, and how often to apply. Thanks in advance for your help.

Cuyahoga County Ohio

Expert Response

Hello,

Would you please send the picture you showed the nursery staff and let me know the fungicide they recommended? To answer your question thoroughly I would like to see the cedar apple rust on the juniper trees. If you wouldn't mind please include a some pictures of the entire stand of trees or individual trees and their location. Thank you,

Sabine

Sabine Kuhn Replied May 23, 2023, 7:02 PM EDT
Sorry, forgot the pics. Please find attached. They recommended trying to pull the fungus off and the spraying with Bonide Fung-onil. I didn’t do that for fear of spreading the fungus and my thought was to try and spray. But I wanted to ask the extension first. As you can see they are filled with it.

 So it rained on Saturday and they created that orange bloom on the branches and that’s when I first noticed them. Today I noticed that there are areas where the needles look burnt brown. They look like they have dead spots and the trees just look unhealthy. I wrap them in winter and feed every spring and fall. They are well cared for. My other thought was whether it might help to cut the branches back a little to create more air flow since they are large and have gotten close together. By the way we do not have any crabapple tree or apple trees in our yard or in adjacent yards, but I’m sure there are crabapples in our neighborhood. They are prolific in this area. Appreciate any suggestions you might have. Thanks.

Linda


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On May 23, 2023, at 7:02 PM, Ask Extension <<personal data hidden>> wrote:


The Question Asker Replied May 24, 2023, 11:01 AM EDT

Linda,

Thank you for sending the pictures and the additional information. Your junipers definitely have apple cedar rust, Gymnosporangium juniperi-virginianae. Ohio State has a good fact sheet on this disease. https://ohioline.osu.edu/factsheet/plpath-tree-10. The appearance of the gelatinous orange growths is to be expected when the juniper is infected with the pathogen that causes apple cedar rust. They usually appear after a steady rain. During a dry spell they'll shrivel up only to expand again with the next rain. Unfortunately the majority of the literature on this topic is about treating apple and crabapple trees and recommends against treating junipers (see links below). The condition is of concern to apple orchards since their crop can be destroyed by the fungus. 

The apple cedar rust does not kill the junipers but can be unsightly. A heavy infestation can lead to branch or twig death, which is what you are seeing. Removal of the galls is a possibility but may disfigure your trees. If you do decide to cut some of the growth out, make sure to sanitize your pruners with disinfectant after any cut to avoid spreading the fungus.

Treatment: The majority of the research-based literature I read indicated to not treat the junipers with any fungicide.  https://extension.umn.edu/plant-diseases/cedar-apple-rust#symptoms-on-apple%2C-crabapple%2C-hawthorn-and-other-plants-in-the-rosaceae-family-1173260.  Oklahoma State University also indicated that but mentioned a fungicide schedule for cedars if desired.  https://extension.okstate.edu/fact-sheets/cedar-apple-rust.html#control. This link https://extension.okstate.edu/e-pest-alerts/site-files/documents/2010/plant-disease-corner-april-2010-april-28-2010.pdf list some of the fungicides that can be used on eastern red cedar. From your pictures, I am pretty sure your juniper is a eastern red cedar, Juniperus virginiana. 

I read the detailed product label for Bonide Fung-onil. It is a broad spectrum fungicide that does treat Gymnosporangium spp. , however apple cedar rust was not specifically listed. https://files.plytix.com/api/v1.1/file/public_files/pim/private/assets/43/37/8d/5e/5e8d3743202d9eba64d3af60/texts/2d/9b/42/60/60429b2d73995a2d5bbf01ff/l880.pdf 

I hope this is useful. I am a Master Gardner Volunteer and not an expert on fungicide treatments. If you would like additional information, please respond back.

Thanks,  Sabine


Sabine Kuhn Replied May 24, 2023, 7:38 PM EDT
Hi Sabine,

Thank you for the information. I’m so sad for these trees. They look disfigured and I can see where the galls have dissipated the branches are being damaged. I have two varieties of junipers- Wichita Blue and Moonglow. I’m not sure if these are Eastern Red Cedars or not? Also, a few more questions I have-

1. Can I expect this dieback to occur wherever the galls are because they are everywhere. I can imagine if it keeps getting reinfested every year it will look unsightly and pretty much kill the tree.

2. I read online that a Copper Fungicide by Bonide might work better for treating this. Any thoughts on that? 

3. Also one of the fungicides listed is Neem oil. I have neem oil and typically spray these trees in the summer with it. I wonder if I could make my own spray with neem oil to treat this? 

4. I’m going to try my best to save these trees and I will start treating them right away until September. If in the worst case scenario I need to rip these trees out and replant is there a variety of juniper that isn’t susceptible to this fungus?  Or maybe there is something else I can plant for privacy that is deer resistant and grows up to 15 ft tall?

Thanks again.

Linda

On May 24, 2023, at 7:38 PM, Ask Extension <<personal data hidden>> wrote:


The Question Asker Replied May 24, 2023, 11:43 PM EDT

Hi Linda,

I'll get right to the point. Your junipers are cultivars of Juniperus scopulorum. The literature I sent yesterday applies to them.

On 1) Based on the life cycle of apple cedar rust, the disease needs to go from your junipers to apples/crabapples before the junipers can get reinfected. The entire life cycle will take 2 years. You can expect some dieback where the galls are currently. I cannot say how much, it's a bit of a wait and see.

2) and 3) the Bonide Copper fungicide and neem oil can be used to treat apple cedar rust. Searching the detail product label, the listed applications for rusts but not specifically apple cedar rust.  https://files.plytix.com/api/v1.1/file/public_files/pim/private/assets/43/37/8d/5e/5e8d3743202d9eba64d3af60/texts/f1/7c/5c/60/605c7cf<personal data hidden>d88dfd5/l813.pdf and https://www3.epa.gov/pesticides/chem_search/ppls/<personal data hidden>2-20180531.pdf 

In a publication by the Clemson University extension office I found 2 fungicides that specifically mentioned apple cedar rust rather than rusts in general.  And treatment was indicated for ornamentals, not fruit trees. https://hgic.clemson.edu/factsheet/juniper-diseases-insect-pests/  The two fungicides are Mancozeb (by Bonide)   https://files.plytix.com/api/v1.1/file/public_files/pim/private/assets/43/37/8d/5e/5e8d3743202d9eba64d3af60/texts/16/06/4e/60/604e061656c98b0d2a01ca51/l862.pdf and propiconazole https://www3.epa.gov/pesticides/chem_search/ppls/<personal data hidden>0-20200501.pdf

4) If you should need to replace your junipers, the Clemson article lists a variety of resistant junipers. 

I am keeping my fingers crossed for your trees.

Sabine


Sabine Kuhn Replied May 25, 2023, 4:04 PM EDT
Thank you Sabine! This is such great info. I greatly appreciate it. A couple of final questions-

1. You said the life cycle of the fungus is two years. So does that mean that the apples will not get infected until the next growing season? Which means I shouldn’t see the galls again next spring/summer, but possibly the year after?

2. I’m trying to use as many organic products as possible, so I think I will start with Neem and Copper Fungicide. Is the Bonide Copper Fungicide considered organic? When I read the info on how to spray it they are suggesting using a mask and protective clothing which made me think maybe it’s not organic.

3. Last question, I have roses in my yard could they be allowing this cycle to happen? From what I read plants in the rose family can contribute to the cycle?

These haploid spores, then, are released by the cedar gall. These spores cannot live on cedars: they can only survive on apple or crabapple trees (or their close relatives in the rose family).


Thanks again,

Linda

On May 25, 2023, at 4:04 PM, Ask Extension <<personal data hidden>> wrote:



The Question Asker Replied May 25, 2023, 4:57 PM EDT

Hi Linda,

1) I interpret the life cycle of the cedar apple rust to be as you describe.

2) Bonide copper fungicide is organic. Just because something is organic doesn't mean you shouldn't wear protective gear. Any organic material at high concentration can be toxic. For example, we need to drink water but too much water can cause hyponatremia. Granted we don't need to wear protective equipment to drink it. :-) Neem oil and copper fungicide carry a caution label for application. Here is the link to OSU's pesticide label fact sheet https://ohioline.osu.edu/factsheet/aex-79026 for clarification. 

3) While cedar apple rust affects members of the rose family, this does not include your roses. This reference indicates that the genus affected by the rust are in the Malus (apple) and Crateagus (hawthorn) families and closely related genus, roses are not closely related.  https://cdn.shopify.com/s/files/1/0145/8808/4272/files/A2598.pdf

Lastly, I understand your desire to treat your plants organically, I do the same. However, the research on cedar apple rust does not indicate the best control of the disease with neem oil and copper fungicide. https://hort.extension.wisc.edu/articles/cedar-apple-rust/#:~:text=The%20most%20common%20Gymnosporangium%20rusts,those%20referenced%20in%20their%20names.

Excerpt from above link:

Fungicides treatments are also available to control Gymnosporangium rusts, although such treatments should be considered only as a last resort. Among fungicides marketed for use by home gardeners, those containing chlorothalonil, copper, mancozeb, myclobutanil, propiconazole, and sulfur are labeled for use for Gymnosporangium rust control. These products may be useful for controlling Gymnosporangium rusts on rosaceous hosts, but will likely not be particularly effective if used on junipers.

Sabine

Sabine Kuhn Replied May 25, 2023, 9:55 PM EDT

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