Brown bumps on underside of Phalaenopsis leaves

[tim abbott]

This is not my plant, I saw it while working at someone's house. I have never seen this condition before & was hoping someone could diagnose what it is. The tops of the leaves were covered in small dark specks. The plant appeared to be healthy. Thank you.

[Arizona Jeanie]

Those are scale insects, hunkered down and sucking the juice out of the plant.
For just a few plants, they can be removed and destroyed using a q-tip dipped in rubbing alcohol. Plants should be inspected and re-treated 2-3 times per week for a few weeks, then weekly--forever.
All plants in the house should be inspected and treated if needed, these guys do get around.

[tim abbott]

Thank you Arizona Jeanie. I will pass on this info

Tim Abbott

[Ray]

Yes, it may be treated that way - forever - or your friend can use a systemic insecticide listed for scale to eradicate it altogether.

[tim abbott]

Thank you Ray, I will let her know. This board is a wonderful source of knowledge.

[Arizona Jeanie]

Hi Ray,
Which systemic insecticide do you recommend for scale on orchids? And how do you apply it?
On other plants I've used imidacloprid granules, but they just wash out of the coarse bark potting mix I use for orchids. I've done OK with spot treating with alcohol, but would be interested in other, systemic, options.
Thank you!

[Ray]

I use Acephate when the plants are outdoors or in a separate greenhouse (it really stinks!). If you can get a water-soluble imidacloprid product, that’ll work well, as well. Concentrated azadirachtin products are also effective.

In all cases, I spray all the plants, wetting all exposed surfaces to dripping, and thoroughly drench the potting media. Do that three times at one-week intervals.

If, within about a month, you see a return, repeat that regimen using an insecticide with a different MOA.