Identify this issue please
 

I don't dare to call it a disease yet, but i'm really confused at this moment. It may be related to an organic fertilizer but it may not. I had started using an "organic" fertilizer that left my green house smelling like a pier at the beach. I guess it contained fish oil, but I stopped because it was plugging up my sprayer. Not long after I started noticing black waxy spots on one of one of my laelias, and later dendrobium and a couple of others. First I thought it was secretions from the plant and dirt was sticking to it, but then I started noticing more and more spots and on others. If I grab the leaf i can scrape it off with my nail. Some are more stubborn than others, and it kind of leaves a tender spot where it was removed. I tried spraying physan 20 thinking it may have been a fungus. The weird thing is that there are also same size spots on the green house poly panels. The plants seem to be growing and even flowered normally. Any clues as to whats going on.

Hi bmena, and welcome! I wish I could be more help, the pictures are not really clear enough and enlarging makes them blurry. I do not have a greenhouse, others here will be more helpful. To me it looks like algae and if you are able to scrape it off with your nail, you may be able to wipe it off with a damp cloth. You mentioned it also being on the greenhouse poly panels, that makes me think algae as well.

I'm sure other members will have suggestions for you. Sorry I'm not much help.

I agree with Pattywack, it probably is some sort of algae. Physan should knock it down. Also, if the fertilizer is plugging the sprayer, it may have some solids (from kelp or something else) that doesn't actually dissolve. If not dissolved, it certainly isn't going to benefit the plants, just make a mess.

No, don't think is algae. This has been going on for about 5mo +, and yes physan should have taken care of it. Algae is not waxy....and I figured, if it would have been residue from the organic insecticide it should have worn out by now... or at least not propagate. There is no insects, present except the common scale i get some times, but it goes away as soon as I treat it (I went back to my old faithful insecticide). The thing is, i sprayed all my orchids with it. But this seems to have started in one area only and spreading to the next plant...

Sooty Mold?
 

I have not experienced this problem with my orchids but did have a problem with it in my perennial garden outdoors last summer. Research this fungus & see if that might be the issue. The fact you can scrape it off is what tipped me off as to what it could be. Let us know what you find out.

I'm inclined to agree with Sharon. I've seen this in my greenhouse too. The fact that it clogs your sprayed is troubling.