Is there a better method? I know spider mites can get terrible (this plant is trashed!) and don't want them spreading throughout the other houseplants.

Any ideas appreciated.

Do you have any kind of horticultural oils? Can you get any kind of natural sprays that specifically targets mites? Can you get "cold pressed Neem Oil" anywhere?
Can you take it to the shower and wash each leaf off rubbing them between your fingers with very soapy water?
All these will help, plus more..

What kind of mix are they planted in and what air temps are they exposed too?

The plant is not trashed...Not yet..You can beat this..

A 50/50 mix of water and 70% rubbing alcohol provides instant and significant knockdown as a contact spray (it has to contact the mites). Neem oil (ask for recipe if you want it) mixed with water, rubbing alcohol, and a little Murphy's Oil soap works very well.

Dish soap is a poor substitute for the long (hydrocarbon)-chain fatty acid soaps like Safer's, Bonide, Spectrum and others, marketed for their insecticidal properties, so it's best to avoid it.

Al

Al

As long as your roots are suffering in that kind of mix, or will sooner than later, your plant will most likely succumb to mites and other pest related issues because they are drawn to plants that are not growing to their full healthy potential, no matter how many times you treat the part of the plant above the soil line..

This is a big factor in a lack of pest's for me, ever since by trees have been potted in mixes that are very porous and open.

P.s..I should of told you to use a "natural soap", or one's that Al suggested. Rhizzo knows of a couple of natural soaps if she sees this thread..I do not use dish soap myself..I have used what Al suggests in the past.

Now, the manure and sand I use to put in my pots go into my garden beds.

Happy growing.

I often see recipes of various mixtures of dish detergents and other ingredients as equal substitutes for insecticidal soaps, but there is a considerable difference between the two. What we refer to as a soap is a substance made by combining a fat with an alkaloid, like sodium hydroxide, which will yield a hard soap, or potassium hydroxide, which yields a soft or liquid soap, like insecticidal soap(s). Of the wide array of fatty acids often used to make various soaps, only a certain few have the insecticidal properties that give them inherent value to gardeners.

With that thought in mind, and contrary to abundant rumors, you should realize you can't employ common kitchen/dish soaps and expect effectiveness equal to what you can expect from actual insecticidal soaps, like Safer's, Bonide, and other brands. To be sure, most household soaps/detergents are at least mildly phytotoxic, some to a sufficient degree that they can actually kill plants. Do you know which ones might be safe and which ones dangerous to plants?

One of the most fundamentally important chemical properties of soaps used as insecticides are the number of carbon atoms in the hydrocarbon chains. Soaps with many carbon atoms are long-chain (usually potassium) fatty acids and have insecticidal properties. The fatty acids in insecticidal soaps alter the structure and destroy permeability of insect cell membranes. This causes leakage of the cell contents and quickly leads to death of the insect from dehydration. Kitchen/dish soaps are usually formulated for their grease cutting ability and are usually made from a combination of chemicals that yield a detergent, or in some cases from a combination of detergent(s) and a soap made from short-chain fatty acids unsuited to use in insecticides. These soaps are more often than not phytotoxic and can damage leaves and bark by destroying cuticular wax. This puts them more accurately in the category of 'herbicide', rather than 'insecticide'.

Even if the detergent or dish soap itself should prove not to be phytotoxic, dyes and perfumes that are added to these soaps usually are. The frequency with which these additives are altered so the words 'new' and/or 'improved' can be added to the label leaves us unsure whether or not the brand we used today will still cause no apparent issues tomorrow. The soaps for pesticidal applications are safe, tested/proven effective, relatively inexpensive, and a better choice than the home concoctions we so often read about.

Still, it is good practice to test even commercially prepared insecticidal soaps on a part of the plant before spraying it entirely. They work best when mixed with distilled or conditioned water because a precipitate may formed when the metal ions (e.g., Calcium, iron or magnesium) found in hard water bind to the fatty acids in the soap. A short list of some of the plants known to be sensitive to soaps and detergents are J maple, jade, lantana, gardenia, bleeding heart and crown of thorns. Some cultivars of azalea, poinsettia, begonia, impatiens, ferns, palms, and succulents should also be tested.

Al

Very valuable and timely information, not to say reminders really appreciated along with your generous time and offering..

Thank you very for the safety of my plants!
I am very grateful you take the time to stop by here more frequently..This has been a huge reason why I have avoided harming the foliage to my trees and gardenia's like I have in the past..You are so spot on with jades too! You forgot to mention "violets" to that list...lol
You also spare my plants alot of heartache in providing the know how on using fantsatic mixes..Sort of a double blessing..

Mike:-)