I have been battling this pest for years. It is immune to imidicloprid (although it does slow it down). It attacks soft woody plants hibiscus, roses, papaya, and chili peppers. The plants that are not that hard to replace, like the peppers, I usually toss them out. they will survive and produce with the pest, but eventually, it will become more trouble than it is worth. I only have 3 hibiscus, one of them has the scale.
I used to have to scrub the roses with a brush and soapy water, sometimes weekly in summer. I also have to inspect and hose off any scale whenever I see them starting to make a comeback. It has been less of a problem since I planted the insectary garden around the roses. I have seen a lot less of the scale and I don't have to hose off the roses as often.
I have had issues with the organic cucumbers and almost daily rain so I had to use 3 in 1 spray almost weekly for a couple of months. That has impacted the predators because the 3 in 1 spray contains pyrethrins. I have been able to back off on that for the last three weeks, so I think the predators will make a comeback.
In the meantime the snow scale has taken advantage and made a comeback. So, I will have to cut back the hibiscus again, scrub the trunk with a brush, put out ant bait, and coat the plant with horticultural oil in the evening. I am going to try to get some clean cuttings from this plant and start a new one. H. mutabilis is an old fashioned hibiscus but not very commonly seen. So, I need to establish a new clean plant before I get rid of this old one.
https://www.ctahr.hawaii.edu/haraa/HIBI ... PressQ.pdf