Imidacloprid use, especially with houseplants is greatly discouraged because of toxicity concerns, and that many of the target insects are developing immumitites to it, it is simply no longer very effective.
Neem oil sprays seem to be about the most effectgive means of control today.

Here is a link that might be useful: houseplant mealy bug control

greenthumb, your narrative is a classic platform for IPM (Integrated Pest Management) for which there is a special forum.
Consider the following.

1. Reduce the existing population. This is achieved by dabbing the individual insects with alcohol, wiping/washing the plant parts affected or pruning away the badly affected parts.(in ascending order of seriousness)
2. Prevent reinfestation. Seek and destroy the pest from other harborage. You have identified these areas. It is sometimes possible to isolate the plant(s).
3. Repeat steps 1&2 at least weekly.
   I do not recommend the use of chemicals indoors because
   There is no safe chemical; only safe ways of using chemicals.
   Every drug has side effects.
   Is the program easy? I am not promising you that.
   It is very interesting; that is my assurance.

If chemicals scare you, don't read what I have to say.

Because the chemical called neem oil scares me. Okay, it really doesn't, but potential sterility sounds like a rather serious side effect.

To answer the question, labels exist for acephate and permethrin used as systemics. If you are to the point that you are throwing out plants, I'm willing to bet you are willing to try most anything. There are significant potential side effects to both. There is also a label for dinotefuran, which is in the same class as imidacloprid, with the same mode of action, so the potential for resistance is quite real. If you are going to continue to rely upon systemics for control, follow one of the cardinal rules for control: rotation. Rotate mode of action, rotate class of chemical.

The first thing that crossed my mind was that it may be time to try a dormant oil. Second thing was a really big tub and total immersion therapy. Not sure how hoya respond to dormant oil.

In my experience, which is valid only for me, the plants I grow and the conditions under which I have tried it, alcohol works as an attractor for mealybugs. I will admit, I gave up using it after about eighteen months. I really should have given it a thorough testing. My alternative, which again, is only applicable to my situation, was cryptolaemus. Not sure I'd use it in a house.

greenthumb, I did not mean to scare anyone. I always advise great caution for the two reasons I emphasized. The modern structure is almost hermetically sealed. In the home, there are enough "pollutants" in the form of VOC's and the like. We do not need to add to that load by applying chemicals to indoor plants.
And I will repeat:
There is no safe chemical; only safe ways of using chemicals.
Every drug has side effects.Color>

Thanks, all!

For now, I will just have to wait until the weather gets warmer out and then EVERYTHING will go outside to be sprayed with Malathion or some other nasty thing. I have to try to get rid of these bugs. Once the bugs are gone, I will never bring a new plant into my home again! (probably easier said than done)!

greenthumb, aw, come on. Have you never heard them say, "Never say 'Never!'?
In this case, there is no need to. Treat your home as a country; and plant yourself as the "Customs & Plant Quarantine Department" at each port of entry. You catch my drift?
Inspect each plant, (even the one that you put outside to catch a change of air) for any sign of infestation or infection. A quarantine station can be made by draping a garbage bag over a tomato cage. Treat the plant and place it under this cover for a day or two and run a final inspection before you bring it into the house.
And malathion is not a nasty thing. "DDT" (banned) and "Lindane" (still in use?) were active ingredients in treatments for lice and scabies on human beings.
"The danger is in the dose."

Malathion, while rated as having low toxicity to humans, has had varying results in research. Some researchers have found no great harm done while others have seen indications there may be. Malathion is a broad spectrum poison that should be used and handled with great care.
Any product that kills insects, including Neem products, could potentially do harm to us, so due care in using any of them is well warranted. People in India have been using the various products from the tree they get Neem oil from for centuries, using the bark for tooth brushes for example, with no adverse affects.

greenthumb, I did not mean to insinuate that 'malathion' is safe. It is a chemical and - "There is no safe chemical....."
The main point is that the Dose determines whether or not 'Malathion' (or any chemical) is safe in a particular application.
And, to illustrate the point, I mentioned the use of DDT1944, and Lindane ; both chlorinated hydrocarbons and used on humans.
The discussion is old; very old. Check out this rumor.

i will add one thing.. for those who are browsing.. but havent done all this.. that has been left unsaid above ...

when i use chemicals on house plants.. i do it in early fall .... OUTSIDE ... which gives the plants/pots.. at least a full month OUTDOORS to off gas.. and get rid of the chemical smells.. and reduce to nill any lingering chems in the house ...

i also do it for all houseplants that spend summer outdoors .. so as to avoid bringing in a plethora of bugs as winter guests ...

and i usually repot/change media ... a week or two earlier ... also reducing bugs in the potting media ... and that would be part of the IPM [integrated pest management] mentioned way up top ... [and i never use chems on a stressed plant -- so repot first.. let it calm down.. then go for the systemic]

anyone who does this entirely in the house in winter when the house is hermetically sealed ... ought to rethink proper timing of preventative medicine ... if you prevent.. you dont need to cure at the wrong time or wrong circumstances

ken

One very effective method of insect pest control for any plant is to give it a good shower, knock those bugs off the plant. That also does not expose you and your family to the potentially bad side affects of the poisons many people use which we have no real idea what they do. Very few of the poisons sold have been tested for adverse affects to humans because there is no requirement to do so because they are not meant to be used on humans.

GT,

"It will kill the young mealies, for a while, but the adults don't die unless I spray them with a 50/50 mix of 70% rubbing alcohol and water with a squirt of Ivory dish soap added."

The adult mealies are probably not feeding significantly, if at all, so they don't get a dose of any systemic. I think you are going to have to resort to some sort of contact killer, like alcohol & water or some actual contact insecticide to get the adults. I have on occasions used a household vacuum cleaner or a computer keyboard vacuum to suck insects off of my plants.

"Does anyone know of another systemic available that does not contain Imidacloprid?"

I am going to rely on Kontos as a first line of defense against aphids, thrips, and spider mites on my indoors zinnia activities. It travels both up and down in a plant, so you don't have to spray it on -- you can apply it as a drench or just include it in the water that you use on your plants. As far as I know, it is the only fully systemic miticide. Yes, it is expensive. But not as expensive as Forbid. Obviously, you should not use any systemic on an edible plant.

ZM
(not associated with any product or vendor mentioned or linked)

Di-Syston is a systemic insecticide. I haven't bought it in a few years, but the container I have on hand was made by Hy-Yield.

I think the Di-Syston product was discontinued and withdrawn from the market several years ago.