Well, anyway, it's new to me, and I'm just horrified!
To start at the beginning, about ten days ago I put the overwintered plants out onto the deck in a sheltered place to acclimatize. Along with my small but growing collection of agaves, I put out the Meyer lemon. It's still blooming nicely, by the way.
Today, I was checking the potted plants for moisture. I noticed ants had discovered the sticky, sweet nectar of the lemon blossoms and were busily traveling up and down the tree's trunk to gather it. I wasn't crazy about that (the next step is an aphid farm, in my experience), but then I noticed something very different on the stems.
I had never seen scale before, but my heart just knew that's what it had to be.
By the time I took these pictures I had removed as many as 50 scale ranging from 1/16" to 3/16" in length.
Now here's the scary part: suddenly I noticed more. A lot more. Look carefully and you'll see those are all tiny scale insects down the center of the leaf and in some of the side veins above. And that's not the only leaf affected. These pests are all over our poor little tree and they seem to be in all sizes, including microscopic - those females have been busy over the last ten days.