[Cynthia, Prescott, AZ]

It looks very much to me like scale to me. Don't think its mealies Mike. Look at the largest of the spots. Are they round? Do they nudge off with a finger nail as a thin papery disc? Some scale make high half spherical shells, but these look like the flat type. However, Mikes solution is very good for scale too, so look for the Bayer Advanced Rose & Flower if your problem is small enough for a ready mix bottle. Or you could use the Bayer Advanced Tree & Srub and mix it at 2 Tablespoons per gallon to make the equivalent of the ready mixed product (you might want to check my math by looking at the % in each product and figure what gives the same concentration of the imidacloprid in each). Spray the plant well, and some in the pot won't hurt. And if you mix the concentrate, you can aford to put a lot in the pot to be taken up by the roots. Keep a very close eye on your other plants for these beasts. They usually start as little crawlers that like to be near the base of the psuedobulb, and that is what killed that one discolored bulb. Scale uncheck is a real killer, not just a nuisance.