Black Spots on Underside of Den. Leaves
 

I have a few dendrobiums that have a weird black spotting on the bottom of some of their leaves. I've included a pic of my Den. spectabile cross as a representative sample.

On the top of the leaves there are few, if any spots; this occurs on the bottom of the leaves.

I have recently posted about my mealybug infestation, which I have treated with insecticidal soap and insecticide (specifically first with tebuconazole, tau-fluvalinate combination then with imidacloprid) and I have also treated with a spray fungicide prior to the insecticide treatment.

The black dots were present before treatments and whatever spread may have been happening seems to have stopped or at least slowed significantly post treatment.

I've scoured the web and orchid board trying to determine what these spots are, since they are predominantly on bottom of the leaves.

Frankly, all, I'm feeling a lot flustered and frustrated with my issues I've had lately. It seemed like problems went from nothing to explosion. Yes, I'm learning a LOT from all of this, and I am sincerely grateful for all the advice here. Hopefully I'm not being hypersensitive now and causing more problems.

If it isn't spreading, I think time to chill a bit. Once stuff occurs, the leaves aren't going to look pristine, but then, none of us is perfect... (I have lots of ugly leaves) It sounds like you have gained control and containment, which is great. Just stay vigilant but don't stress about every spot. (Like raising kids... parents soon learn that a sneeze doesn't mean pneumonia )

Might be damage from previous insect bites. Focus on providing proper temperatures and light, reasonable humidity and proper watering. You will have fewer problems.

Roberta and Estación, thank you for your words of advice. I had wondered if the black spots underneath leaves were injuries from insects.

But, you're both correct: focus on maintaining a good environment and sticking to a "program" to treat an issue will get me a lot further than freaking out on a problem -- and letting that problem grow in my mind.

Thank you for your thoughts. I really appreciate it.

And even after all the worry and care, my den. Miva Abracadabra is giving me some hope with this spike it's developing. This isn't the only new growth I'm seeing, but it's a nice new spike.

Most orchids are easy to grow if surrounding conditions are correct. When they struggle it's usually not enough air at the roots, not enough water, or the temperatures and/or humidity are too high or too low.