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The Struggle Is Real, the Solution Surprising: What to Do About Galls

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By Lisa Brunette

It looks like a life form from another planet. But it's definitely terrestrial. Remember that row of evergreen screen trees we planted along our fence line? That was in the fall of 2018, when we had a little help installing a row of nine mature eastern red cedar 'Taylor' trees. This past spring, I discovered massive galls attached to the twigs of many of those trees.

The galls are quite a lot to take in when you first notice them, even in their dry state, as in the above photo. I guess it's a natural human reaction to become simultaneously disgusted and fascinated by things like that, sort of like when you keep flipping through an illustrated book on tropical skin diseases, unable to look away. We've all been there. So it was with equal measures of horror and curiosity that I began to monitor the gall situation. They first appeared in the middle of our rainy spring, and believe me, they are even more startling during wet weather, when the "teliohorns," as they're called, swell and ooze.

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It's not just a girl thing, either. My brother came by during this time, and he thought I should cut them off the trees, immediately. Anthony was likewise a bit disturbed.

But trying to remove the galls would only spread the spores. While some tree galls are the result of insect activity (feeding or laying eggs), the ones taking up residence in our cedar trees are a type of fungus. The fungus produces growths on the cedar's twig tissues, similarly to warts on human skin. Yeah, does that make it better for you?

If removing the galls isn't the right move, what should you do? The answer: nothing. The fungus doesn't actually hurt the cedar trees. They carry on as if they can spare a few twigs, no problem. So as long as you can handle the sight of those oozy teliohorns emerging out of a shiny sphere like some kind of alien invasion in your garden, it's all to the good.

But this thing isn't called 'cedar-apple rust' for nothing. The issue is the fungus has a two-host life cycle, and the second host is usually a plant in the rose family, particularly apples. 

Now, I had been warned about combining eastern red cedar with an orchard for this very reason, but I'd avoided any issues by choosing disease-resistant apple varieties, such as Arkansas black. It has withstood the spore invasion valiantly. 

But then... I slipped up.

Cedar rust on leaves

I bought a Rome beauty on an impulse, momentarily forgetting it is susceptible to cedar-apple rust. In my defense, it is a good pollinator for the aforementioned Arkansas black, and more suitable as an off-the-tree eating apple than the black, which can be hard and tart. But, yeah, when the galls moved in, the Rome beauty's leaves picked up the rust.

Unfortunately, so did one (but not both) of our serviceberries. I didn't even know cedar rust could infect serviceberries. That one sunk me low. Have you ever eaten a serviceberry? They are delicious, kind of like a combo strawberry/blueberry, only sweeter, but not when they're covered in rust. Just the sight of those teliohorns oozing out of a berry is enough to put you off. Sorry I don't have a photo; I was too sad to take one.

I did not want to use a fungicide to combat the rust since our garden is 100 percent organic; besides, by this point, the rust had already infected the leaves, so it was too late since fungicides work only as a preventative.

Then I remembered an interesting post I'd tripped across previously on a permaculture forum called Permies.com... something about using plumber's tape to combat cedar rust. I retraced my steps and found the post again: It was by someone in the Midwest, in Missouri as well, in fact, who discovered that his home's cedar shingles did not develop cedar rust even when he tried to inoculate them with the fungus. He surmised that the shingle's resistance stemmed from the introduction of metal-frame windows, which act as a kind of fungicide, due to the oxidation from the aluminum, zinc, titanium, and trace lead in the metal windows. He was able to reproduce this effect on his fruit trees with plumber's tape:

...If I attach a piece of plumber's tape (about four inches worth) to the top of the tree, the tree does not develop the fungus.  Plumber's tape is made primarily of lead, zinc and aluminum.  The rain causes the tape to slowly, ever so slowly, rust and the oxidized compound is slowly distributed over the central trunk and the top branches.  Because of the nature and shape of the tree, this same "rust" gets dusted all over the rest of the tree.  Result - just enough anti-fungal action to stop the Cedar/Apple fungus. 

What the hell, I thought, might as well try it. I ordered a coil of plumber's tape and a pair of tin snips and went to work. 

I don't know - this might have saved the Rome beauty! Once I placed the plumber's tape on the tree, the rust ceased to spread. It was early spring at this point, and all of the tree's new growth came in 100 percent without rust, including our first apple. In the next two photos, you can see the rust on the leaves below the tape, but not above it, and the apple is free of rust.

Plumber's tape

Apple

Boosted by that success, Anthony and I took the time to wrap every cedar tree plus every susceptible fruit tree (not just the serviceberry and apple, but the persimmon, too) in plumber's tape. All of the trees are now healthy, and any sign of rust from the spring has given way to fungus-free new growth.

The method checks out as safe; here's this from the original poster on Permies.com:

I have not been able to detect any heavy metal depositing in the soil around the trees (or the house for that matter).  This is a good thing, because I don't want to contaminate my soil.

As you can imagine, I'm quite relieved to see this seemingly crazy, home-grown solution worked. For a while there, I worried we would have to remove all of the cedars. They were planted in a dry, rocky strip that once served as a gravel drive to a garage that is no longer standing, and they took to it with vigor; most other trees would not. They also have high value both to wildlife (as both food and shelter) and to us (as a privacy screen and source of food and medicine, and potentially, wood).

By the way, as an interesting side note, the fungus only took up residence in the 'nativar,' a somewhat cultivated variety called 'Taylor,' but not in either of the true native Juniperus virginianas.

I'm not sure if we'll see the galls return or not next spring, and if they do, whether or not the spores will infect the fruit trees. Our other defense is an increasingly biodiverse 'food forest,' which should also help buffer against the rust. But in the meantime, I humbly give respect to the evolutionary process that produced Gymnosporangium juniperivirginianae. I appreciate its strange... dare I say? Yes: beauty.

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