I have a beginner's question. Several of my plants (an oncidium and an
odontoglossum) have developed black spots on the leaves. I gather from what
I've read here and elsewhere that Physan spray may be helpful. I have the
physan; what dilution should I use? The label says 2 teaspoons per 20
gallons. That's the weakest dilution I've seen. In looking at various
sources on the web I see dilutions as high as one tablespoon per gallon, and
everything in between. It seems that stronger dilutions are appropriate for
use on non-plant surfaces (e.g. greenhouse benches, etc.), but the
recommendations for what to use on the plants themselves are still all over
the place. What's commonly done by posters on this group? Thanks in advance
for your help.
Chuck B.