So let's start by asking a question - where did the scale come from in the beginning? From the environment...from the air, from outdoors, "out of the everywhere into the here." Meaning, the bugs are already around you. You did well to control them on your houseplants, now don't worry so much. If you want to put the plants outside, go right ahead. There are predators out there that control them most of the time. The reason you saw ants in your plants (oh gosh, I said a funny) is that the ants were feeding on the honeydew excreted by the scale, much like aphids, aphids and scale being in the same order of insects. Yes, you should discard the potting medium the infested plants were in, because of the possible presence of eggs. Also the pots that you used should be thoroughly washed and disinfected with a dilute solution of bleach. You should do this with old pots before putting in new plants anyway.

About pests with rasping/sucking mouth parts. I have 4.95 lbs of Marathon, which is a granular product that makes the insecticide imidacloprid systemically available via the root pathway - essentially the same product linked to a couple of posts upthread. I won't use it again because of the negative impact on root health I've witnessed when using the granular vehicle. A better and faster acting product (still employs imidacloprid as the active insecticide) is Bayer Advanced 3-In-1 Insect, Disease, and Mite Control. Used topically (outdoors) in the early morning and left in the shade for a day, it's absorbed into the plant much faster than soil drenches and granular products that use the root pathway. It also contains a very effective systemic fungicide (tebuconazole) that works efficaciously on most varieties of fungaluglies. If you're concerned about bees, don't apply to blooming plants. There is nothing wrong (from the plant's perspective) with using imidacloprid that's delivered via the root pathway; however, I've found the 1.47% liquid soil drench used for trees and shrubs, diluted to 1 teaspoon in a qt/liter of water to be far superior to any granular product I've used, for reasons mentioned. Soil drench. Al

Bal, I cant testify to the Neem OIl...that is suggested to treat black spot and mildew on roses; you might try it. But the oil you are familiar with when applying to your outdoor deciduous trees, shrubs and roses..."dormant oil" is another suggestion. Do read the label. Also suggested is the "lime sulfur"...the other half of the dormant oil application. Smelly stuff this...so open a window and do read the label. No success with soap. Perhaps you didn't do the routine as best prescribed. A 40 to 1 solution dishsoap and water, spray from top to bottom, bottom to top, leave on for 10 - 15 minutes...then rinse well in clear water. To avoid overwatering the surface soil, you might tip the plant to a 45 degree angle or cover with plastic when applying Anytime you have a problem with a pest, it is usually prescribed to treat the plant as many times as needed to break the cycle of the pest's ability to produce larvae. In a 20 day period, treat the plant 3 times. Scale insect does not as far as I know, ever go to the roots, they feed on leaves and stem, sucking the juices there. They leave behind their secretion called "honeydew"...a shiny appearance on the leaves can be seen.

Andy I feel your pain I had scale on some indoor plants over and over. I use Ortho Malathion Plus Insect Spray Concentrate now and nnever saw scales again. Make sure you spry the soil also because the youn scale live there.