Cedar apple rust

[bonsaibandit]

I have a few crabapple bonsai and one Washington hawthorn seedling that just developed what looks like cedar apple rust. I keep my junipers (two itoigawa and one kishu) in my back yard, maybe 100 feet away from the apples. I really like my junipers but only like one of the crabapples (which I am growing out but has a 1.5 inch base and good movement with potential). Would you just throw out all the crabapple trees? Or are itoiwaga and kishu generally resistant to cedar apple rust? Of note my house is a few hundred yards from a park which has numerous crabapple trees (so the cedar apple rust is probably everywhere)

 

[Paradox]

If you have crabapples near your area, getting rid of the one you have probably isnt going to help you much.
The only thing you can do for your juniper and and hawthorn is to treat for fungus to try to keep ahead of it.
Cedar Apple rust needs both junipers and apple trees in the area to be able to complete its life cycle.
What Im not sure of is where on the side of the life cycle of the fungus the hawthorne is. Since its a fruit bearing tree, Id assume its the same side as the crab apples so it will still be an issue.

 

[Orion_metalhead]

I have not had cedar apple rust on any of my shimpaku. I can assumr kishu and itoigawa would be similar.

I have had it on otger juniper in my yard and I have several crabapples on my bench. they are only a few feet from my shimpaku.

 

[Paradox]

Looked it up and saw there is a cedar hawthorn rust. Not sure if it might be related to cedar apple rust

Cedar-Hawthorn Rust

 

[MrFancyPlants]

I have not had cedar apple rust on any of my shimpaku. I can assumr kishu and itoigawa would be similar.

I have had it on otger juniper in my yard and I have several crabapples on my bench. they are only a few feet from my shimpaku.

My ‘blue chip’ did get some jelly when we were in MD. A beautiful full size crab apple was a couple blocks aways. Blue Chip recovered well when we moved. Kishu or maybe standard shimpaku never showed and symptoms of rust, but it also is showing much more vigor since we moved.

I think my procumbens was killed by rust, but it could have been a vacation watering incident or combination of rust and water stress.

 

[Paradox]

I've had it on new procumbens. Since cedar I don't have any apple trees, it didn't go further. I saw the pea sized nodules in the winter and cut them all off and treated if I saw the jelly in the spring.

 

[bonsaibandit]

Thanks for the responses all. That is very reassuring to hear @Orion_metalhead , I had read online that shimpaku were resistant but always good to get confirmation that this holds true in bonsai cultivation.

 

[Leo in N E Illinois]

Just to "pile on"
@Orion_metalhead is correct Shimpaku, Itoigawa, and Kishu junipers are more resistant to the various "rusts" than any other species of Juniper. There are many disease rusts, one for just about every fruit tree, cedar-apple, cedar-pear, cedar-hawthorn and the list goes on. The native junipers are most susceptible in North America. Juniperus virginiana is a rust magnate, and this factor alone is a reason to avoid using as bonsai.

Procumbens juniper is slightly prone to rusts, in areas with heavy disease load, should be avoided. Western junipers and Sierra junipers will catch the rusts fairly easily in the humid east and south.

Some have used fungicides like Mancozeb and claimed success.

I have never been able to successfully treat the Juniper nor the Malus Rust is one reason I do not grow North American native junipers.

 

[Wires_Guy_wires]

I've looked into spot treating juniper rust with fungicides coupled with cell-passing carrier solvents and it did not work.
There's a French company bought up by Koppert that claims they produce an extract that would be able to kill rust disease. I emailed them for a look into their data or to at least get a list of species they tested.
I never got a response.
They should go commercial in the next year, but as with trichoderma, and probio, and all these other biological treatment companies, it seems to be a hit and miss that mostly misses.

Shimpaku junipers specifically seem to grow a black fungus on their bark. I dug into that one and there are a couple that live on plants and eat other fungi. I think shimpaku is not more resistant, but rather have commensal fungi protecting them by creating something favorable that other junipers don't. I'm looking into isolating it, and see if I can tame it. But again, it'll probably be a miss.