Something is killing my Cattleya

[desertgal]

I have no idea what is killing my cattleya. I have taken the best pictures that I can. There is something piling up like a white powder and there are little white spots on the leaves that easily come off. The leaf that is dead had it very bad about a month ago. I cleaned the plant with alcohol and thought it had taken care of things, but the leaf died and the white things are back. I've isolated the plant and am counting on the forum to help me.
It seem to be worse at the base of the leaves. The plant is planted in lava rock.

Katie

[mayres]

The only thing I can relate to (it is difficult to say from looking at the pics - a close up would be more definitive) is mealy bugs. I would get a spray bottle of ready to use Bayer Rose and Flower Spray - it is systemic and seems to work fairly good on my orchids with similar issues.

[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.

[arleneg]

I've been battling these scales for the last few months and lost one catt. It was too late for that one. However, I was able to catch the scales on my second catt. I wiped the catt down with alcohol as much as I can. Then took the catt out of the pot and soaked the roots (up to where I couldn't reach the rest of the scales) in neem oil solution for 10-15 minutes. Thereafter, I repotted the (second) catt in new potting medium and pot. It's been two months (or so). I lost a few leaves and bulbs. But my catt is doing better...has new growths. I just hope I've seen the last of those pests.

[Ellen]

From the pics it looks like you have some rot going on in addition to the scale. It appears that one mature growth and one new lead are black, and there is yellowing at the base of another lead. It's possible that the scale found an easy victim in a plant that was already weakened by rot. What I would recommend is removing all the black tissue and treating with Physan and/or coating the cut edges with cinnamon powder. Also do what Cynthia says (always do what Cynthia says!) and treat the scale with one of the Bayer products. You may need more than one application to kill it all. Make sure you isolate this plant from the others in your collection until you are sure it is healthy again. Best wishes for a speedy recovery!

[Cynthia, Prescott, AZ]

In my experience, scale IS the cause of rot. This is one of the reasons scale can be so deadly. It both weakens the plant, to the point of the yellowing, and provides access to the rot bacteria. Scale does not need a weaken plant to attack. But, as Ellen says, removing the rotted portions is a good idea.