Imidicloprid, avoid products that also include fertilizers. Dilute concentrate (1.47%) 1 ounce (2 TBS) per gallon or 115 ppm.

I've had no luck getting rid of scale on Euphorbias...luckily I only had to deal with it once, on a plant of E. spinea.

Brad, is this from personal experience?

Because I found imidacloprid to be completely useless with scale. Nor were mechanical removal, horticultural soap, repeated alcohol sprayings and dips helpful. After trying to treat it for two years, I gave up and trashed the plant.

Luckily over a few years I've only had to deal with it once.

-R

-R
Yes, I've had some success with imidicloprid, although the scales often remain on the plant. I'm pretty sure they are dead, the infestation stops spreading. They can be scrubbed off, but the damage to the plant makes that approach less attractive.

Scale is rare here too. I've had it on Cacti, Echeveria stems, Euphorbia, and my lemon trees. Mealies are my bane. Imidicloprid completely eliminates them.

Brad