This is one thing you must absolutely know about Junipers and disease

First off, I love trees and I also love fungi. Both are incredibly magical and beautiful. The interactions between these two life forms can be both beneficial but also detrimental. I recently became concerned that some of my Junipers had been experiencing the detrimental side of that relationship as their growing tips began turning a brown color and swelling.

If there is one thing you need to know about Junipers, it’s that these swellings on the growing tips of Junipers are not disease, they are pollen cones. I know this is probably funny to most experienced growers of Junipers but this is honestly the first season I have had any of my Junipers produced pollen cones. And for the life of me I thought that these looked unhealthy. So I broke out my microscope and dove into trying to figure out what was going on.

In my defense, this disease, Cedar-Apple Rust or Juniper-Hawthorn Rust, is on my mind. Most of the Apple trees in my orchard and all of the Hawthorn’s growing on my property have been infected by this heteroecious rust fungi requiring two unrelated hosts to complete their life cycle.

I was elated to learn that my recently collected Rocky Mountain Juniper was actually healthy and not being decimated by a fungal infection. I also then immediately felt silly for not knowing what a Juniper pollen cone looked like. But hey, at the end of the day I learned something and I am ready to play defense for my trees when the rust fungi make attempts to take hold on my yamadori Junipers.

Here are some pictures of the pollen cones and pollen grains under the microscope. Also the last few photos are of my Apple trees and Hawthorns growing all around my Juniper trees. The Fungus is Among Us!


Here is a stand back view of the RMJ and my Apples, and also you can see the humidity in the air which explains why this rust thrives here.


Hello. What do you treat the rust with?
Thanks in advance.

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Per Ryan’s mention of it, I have used Daconil as a way to prevent spores from taking hold on this years growth. Not sure about Daconil’s claims that it can “stop” infection, but I hope that it will prevent new growth being inoculated with spores and can provide my collected trees a chance to build strength/health on their own. Time will tell. I am not treating any of the trees in the orchard or woods around me.

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