I was given a nice minature shefflera that was loaded with scales. I hand cleaned every leaf on the top and bottom to remove them. They are back now. Do they live in the soil?
You can treat them with horticultural oil that is labeled either 'perfect', 'summer', or 'all season'. You can mix it in a hand spritzer or a pump sprayer. Take the plant outdoors (when temps allow) and be sure that the entire plant - every nook and cranny - top and bottom of leaves - is thoroughly covered. That should take care of them.
Zack...I use Fish Emulsion as a Scale preventative and insecticide.
If you decide to go with FE, the dossage is 1 capful per 16oz spayer of water. Leftover mix must be discarded. A second application might be needed.
If your Scheff was near other plants, give them a spray, too.
FE is safe, organic and can be sprayed in or outdoors.
I was given this recipie by a woman in Fl who owns a citrus nursery. They spray their trees w/FE. Toni
Zackey, you just thought you got rid of all the scale. That's not likely to happen, especially with hand cleaning.
The advice about using an oil is your best route. Oils smother scale eggs, scale nymphs (crawlers), as well as the adults. Horticultural oils are also safe and organic. Al suggested that you move the plant outside to spray just to avoid the mess. Once the dripping stops you can bring the plant back inside.
Scale insects do not live in nor hide in the soil. You simply missed some of the very small crawlers or eggs when you did you cleaning. The oil mists will take care of them, especially when applied once or twice a year even if you see no scale.
..... and what Dori said applies to mealybug, too. You just aren't going to even come close to getting them all by hand picking or using a Q-tip dipped in alcohol. You need to have a more effective plan.