Great idea for this thread, Melissa. I've got it all, fungus, insects and even the odd snail. As Jim says, lots of space between the plants for air movement seems to help the most.
But to be honest mites are the one thing I have not had any trouble with on my orchids. I think it's because up until last summer, I had a big Brugmansia growing inside the pool cage and it was an absolute magnet for spider mites. A sacrificial plant, so to speak. Recommend you get a cutting or two for this purpose, Melissa. They will act like the canary in the coal mine for you in your greenhouse.
This year I've discovered through another thread here on blessed ATP that to break the life cycle of mites, all it takes is a brisk hosing with water about twice a week for a couple of weeks. You need to do it at least twice in a row to get the next generation of mites that hatch out after the parents have been killed off. It's the same with the soapy water treatment I was using before, but this is even easier! The Brugs, now living outside in the jungle, have not had an issue with mites all summer! Just get a good bath with the hose at least weekly.
I've had much less scale this year, since using Ursula's treatment of dormant oil spray a few times in the spring. But . . . well it's been wet and humid now for at least a couple of weeks and the black rot is popping up left and right.
To make matters worse, I am going to visit the grandkids in Salt Lake for 10 days starting Monday, so I doubt if DH will be depended upon to spot 'chids with black spots. So, I may come home to a cage full of dead orchids.
