Copper and your orchids

[Ray]

The "French stuff" - known to old-time orchid growers in the US as "Bordeaux Mix" - is a very good bactericide and fungicide, and used to be the "standard" treatment for rots.

It is well-established that copper compounds can damage thin leaved plants - think zygopetalum, as an example), and even Phyton, a commercial fungicide containing copper sulfate pentahydrate (21.4% CuSO4-5H20), should be used with caution on them. I have also heard that paph growers have had issues, as well.