Juniper rust - the solution to rust on a trunk

[Wires_Guy_wires]

I own two collected junipers of substantial size and age.
They came with rust. And since rust needs an intermediate host to spread, I'm not worried at all.

Usually the rust bursts open a few branches every year, I cut those off and the presence has been decreasing every year. However, it's also present in small amounts on the trunk. The trunk I don't want to cut into. Since I've been playing with these junipers for 4 years now, I wanted a solution to just locally kill infections.

This year I ran some trials on six spots with three treatments: roseclear ultra (undiluted), bordeaux mix (copper sulphate and limesulphur) and DMSO.

Roseclear didn't do jack. The fungus kept on growing and fruiting.
Bordeaux mix halted growth, killed the outer layer of the fungus, and it grew straight through a week later.
DMSO immediately spread itself out like a drop of soap in an oily frying pan, penetrated through the bark with ease and straight up murdered the fruiting body and all fungal tissue below in a minute. A day later the rust is shrivelled and crusty. I am still waiting to see if the foliage will be affected so don't get ahead of yourselves just yet.

Don't spray your trees with DMSO. Just, don't. Please don't. But if you ever want to kill individual spots of rust, dip a (preferably wooden, it'll hurt some plastics) q-tip in 100% DMSO and touch the rust with the wetted cotton. Now the rust is dead. One treatment, no antibiotics, no spills, cheap and effective.

 

[Gabler]

What happens if you spray the whole tree?

 

[Wires_Guy_wires]

I seriously don't know what happens if you spray the whole tree. I've read up on 5% DMSO solutions being safe for stuff like lettuce but i'm not sure what would happen.
Since it's a mostly unharmful substance, I expect the damage to be minimal. On the other hand, it eats plastics.. So damaging the cuticle could be a possibility.
I wouldn't be surprised if it would kill foliage.

In a month or so I'll have information on what happens to the tissue connected to the treated spots.

 

[Crazy Diamond]

 

[Wires_Guy_wires]

This chemical is banned from Europe since 2021. And as Bjorn said, the plants need multiple treatments and it's no guarantee that it'll fix anything. That seems to be the tricky part about rust diseases: everyone has something that should fix it, but nobody has something that actually kills it entirely.
DMSO is less toxic to the environment and your little swimmers or embryos and it seems to be a one-touch-total-kill material. So instead of cutting patches from the trunk, you could just hit the pustules with a dab of DMSO and kill the fungus; the DMSO penetrates the bloodstream of the fungus and kills it from the inside out, and the outside in (the magical property of DMSO is that it passes right trough anything, even human skin).

The myclobutanil disturbs ergosterol synthesis but it doesn't kill the fungal body that's already there; it inhibits growth, just like roseclear (triticonazole, also banned in some countries) should do - but doesn't. It's also pretty bad for the soil biome. Since the DMSO isn't sprayed but dabbed with a qtip, it shouldn't interfere with the soil biome at all.

The cool part about DMSO is that it freezes at 19 degrees C. So in fall, winter and large parts of spring here, it turns into a solid. This is pretty handy when you don't want to spill it. But it's also pretty difficult to use it in cold weather if you suffer from cold hands.

I'm not saying it's the absolute answer to rust, but in my opinion killing a fungus with a touch of death is better than having to spray dangerous chemicals four times a year that might not even work. The DMSO will not prevent future infections, but it'll save my 40 year old trunks from degrading further. That's a solid win in my book.

I'm a big fan of Bjorn, but the guy is spraying stuff I wouldn't want my biggest enemies to be close to.

 

[Japonicus]

any chance at finding a cheap trial plant to spray DMSO on?

 

[Wires_Guy_wires]

any chance at finding a cheap trial plant to spray DMSO on?

Yes, but not enough DMSO to spray a plant with..
It's not expensive at all, but I don't really want to buy a full bottle of it.

I'll have a look next week to see if I can water it down to 50% and find a tiny spray flask to use.

 

[Deep Sea Diver]

Echoing. DMSO can be somewhat dicey to humans. So standard chemical use safety equipment, including covering eyes, exposed skin and using gloves.

Here’s the expanded SDS on this chemical.

https://fscimage.fishersci.com/msds/07770.htm

Cheers
DSD sends