Diagnose orchid problem
I'm looking for a diagnosis of what is wrong with my Lori's Star Dedrobium. It appears to develop brown spots on the new leaves emerging from new spikes. If I don't cut off the area of the leaves affected by these spots the whole leaf turns yellow and falls off.
The spots first appear on the underside of the leaves then spread out laterally and on the top of the leaf. Older leaves seem to be affected differently developing spots too but the leaves do not yellow and fall off.
It appears some of my other orchids have this blight too...but are affected differently (and not as bad)
So I have two questions:
1. What am I dealing with?
2. Can I get rid of it, and if so how?
If it is a fungus it appears I will need some sort of systemic treatment (ie that is absorbed into the plant via roots or leaves). I've tried sulphur and sulphur based fungicides to no effect. I live in Canada in the Maritimes. Is there anything I can purchase off the shelf?