Are copper based fungicides harmful to Dendrobium and thin leafed orchids?

[Lupus]

Hello,

a couple of weeks ago I transitioned my cool growing collection from unter lights (because of the summer heat) to my small greenhouse. Last couple of days I have had bacterial and/or fungal problems on some orchids there. I sprayed with Physan20 and after a couple of days also with a systemic fungicide, but some orchids are still affected. So I was considering using a copper based fungicide/bactericide.

So whats the story with the copper and dendrobiums or thin leafed orchids? Here and there you may reed that it is harmful, but I could not find any viable information in the internet.

The only personal experience I have, is with Dendrobium vexillarius, which I sprayed very heavily with a copper fungicide in spring by accident. It was completely drenched and after I noticed, I got very worried. But nothing happened. It bloomed all the time and grew very well and still is.

So is this copper-dendrobium-thing a myth? Or are just some species/sections of dendrobium affected and if so, which? What about Lepanthes or Dracula?

Cheers