It's judgement day for leaf spot.
 

All right. I'm through being mister nice guy with leaf spot. It's having a picnic on my orchids, and I won't tolerate it anymore.

I decided to pull out the big guns, but I need to know which fungicides are safe enough to use on orchids. I'm considering using physan 20 on my plants, but I need to know more about it, and what my other options are.

About a third of my collection is infected as of now, and more plants keep getting infected as time passes. If I can't get rid of the disease, I'll have no choice but to trash and replace the most badly infected plants. I'm hoping I don't have to resort to this, but I'm desperate. :(

wow! no one had anything to say...
ok i will try to help you....physan 20 is pretty harmless to your orchid, i use it all the time with good results for gen bacterial or fungal problems....if you catch them in time they arent too bad to take care of....just mix it according to the instructions, and use it frequently....i use it in a bucket to sterilize my pruning tools, and in a spray bottle to clean any new cuts on plants, and as a 'root wash' to clean out any algae problems....as well as coating any black spot plants whenever i find one...i hope that helps...gl

I use Daconil from Lowes it is in a blue spray bottle seems to do the job .. Gin

consider other aspects of the envionment. Is there adequate and continuous ventilation. is there too much humidity?
If other cultural considrations pass muster, I would go with the strongest recommended for orchids and Daconil is what I'd choose. I'm not as impressed with Physan-20 as a treatment as much as a preventative.
Nick

According to what I've read, Daconil is contact not a systemic fungicide, sold in the UK as a turf fungicide. How do you dose orchids with it, please?

What I get is pre mixed in a spray bottle . There are others Cleary's is a systemic .. Cleary 3336 WP

Thanks Gin

The bottle says active ingredient Chlorothalonil 0.087 %
inert 99.913 <----- water ?? would not be surprised . Gin