Scale insect on Schefflera again and again and again

[Marb67]

For the life of me I just can't get rid of scale insect on this houseplant. I have re-potted in new compost, washed the pot, roots, scrubbed the stem and leaves with a soapy brush and keep in bathroom with no other plants in sight BUT they keep reappearing along the leaf and stem. I do this again and again and yet they always come back. How can this be ?

[Thelma Sanders]

I share your pain! - my Oleander is the same....
You only need to miss one and away they go again. You need a systemic insecticide to stop them and I'm not sure that any are allowed nowadays.....
RHS says this one is still ok to use...

a) Acetamiprid A broad spectrum, systemic and contact action pesticide for use as a foliar spray on ornamental plants. Some formulations can be used on tomato, aubergine, pepper, potato, lettuce, apple, pear, cherry and plum. Also as a compost drench on container grown ornamental plants, primarily against vine weevil grubs. This pesticide also controls aphids, whitefly, scale insects, mealybugs and thrips. The spray formulations can also be used against red spider mite, lily beetle and caterpillars. Sprays containing the fungicide triticonazole also control mildew, rust and blackspot on roses.

Sprays
Bug Clear Ultra concentrate
Rose Clear Ultra concentrate (+ triticonazole*)
Bug Clear Ultra Gun RTU
Rose Clear Ultra Gun RTU (+ triticonazole*)
Rose Clear Ultra concentrate (+ triticonazole*)