Agreed. However, one minor curative that rarely goes amiss is simple mildly soapy water. 1/2-1 tsp in a gallon of water equivalent, spray it on the cutting, and rinse off immediately (I put aluminum foil over the soil). It gets rid of dirt, dust, and minor soft-bodied insects that my visually-impaired eyes simply can't see even with magnification. :-)

Keep an eye on it afterward as that won't kill the more-sturdy eggs of most species.

Do they wipe off easily or are they part of the leaf?

Can't tell from the photos, but scale is usually found near veins.

My question about ease of wiping is designed to diagnose the possibility of scale. But since the excrescences are the same green as the leaf scale seems unlikely.

Thanks, everyone!! I am generally familiar with scale ... but otoh, perhaps there are many kinds.

This was the best I could do. It still doesn't look like anything to me. (I guess scale does make the most sense though. Anyhow, once it stops raining, I guess I'll scrape whatever it is off.)

In the new picture the objects no longer look green, so scale seems more likely.

Yep. You can remove the leaves it's on but that seems to be most of them. I'd try washing the leaves with rubbing alcohol, letting it sit, and washing it off (online recommendation).

I always follow that up with a gentle soap wash to clean the leaves, but that's just me.

Okay, scale it must be then ... thank you, morpheuspa and floral_uk!!!

Baby wipes work well on scale. Recommended to me by a professional citrus grower.