AusBonsai

Hello all,
This summer has been the first time I have ever had myrtle rust on some of my native species bonsai's. It has been so wet and humid in my area (Penrith/Hawkesbury) this summer with a top temperature of 36 degrees. It's never been like this in my 20 years in the area, it's usually really dry heat and a week or 2 of 40+ degrees.
Anyway I'm struggling to find decent upto date information on myrtle rust. I have pruned the diseased foliage off and put it in the red bin, and I have also sprayed infected plants with a fungicide. The fungicide seems to have varying levels of success depending on the species.
I am after advice what others do to treat it
Will it not be present next summer if it's back to our really dry summers?
Will fungicides kill it off for good?
Thanks,
Matt

Hi Matt,
I'm on the mid North coast where it has been very wet, but strangely there has been no rust this year. I'm not sure why? Some if the species that get hit hard are making a come back in the bush.
The fungul sprays work well on bonsai, but it will keep coming back if it is in your area. Keep and eye out and spray as soon as you see it.
Cheers,
Symon

I’m in Ipswich Qld and one of my dwarf Myrtles has it as well. It has been wet and humid here as well. I used Conguard on mine but I suspect I left it too late.

Myrtle rust is endemic now. It’s everywhere across most of the eastern side of Australia and continuing to spread.
You can spray till your hearts content, but you’re just keeping it at bay.

Triforine is the only spray that really works, but it takes its toll on the tree as well.
But more than likely, eventually the myrtle rust will consume whatever you’re growing.

The trick is to grow stock that can tolerate it or outgrow it.
For example, if you grow Agonis flexuosa I have never managed to keep them healthy, as the Myrtle Rust attacks it so quickly, and the tree has very poor resistance to it, that if you have a period of constant rain and low sun, it realy takes hold of the tree.

The problem is that the spores are microscopic, and spread everywhere, lying in wait for optimum conditions to thrive. It’s like trying to spray for covid, eventually someone’s just going to walk back in with more germs.

Then you can also find that the Myrtle Rust itself develops a slight tolerance for triforine. It’s a shocking disease, but natural selection eventually dictates what you can keep healthy.

There are some Eucs and Letpos, and Mels etc that you can grow that will grow well with just a lot of sun and the Myrtle Rust hardly bothers them. But if you have low levels of sun, lots of rain and poor drainage, you’re inviting a cesspool of it.

It can badly affect a lot of myrtaceae varieties.