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



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

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

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).

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