Much safer than indoor pesticides: Exchange the potting mix for new, then avoid excess moisture in the rootball.

The simplest way to eliminate centipedes, or any other soil borne insect, is to replace the potting media the plant is growing in.
Spider Mites can be a bit more difficult. Spider Mites like, and increase in population, on plants in warm and dry environments and increasing the humidity around the plant can help slow them down. Misting the plants a couple, or more, times per day can helps. Giving the plant a shower can also help.
Many insecticides are very broad spectrum and can kill off the predators of Spider Mites so judicious use is needed. Insecticidal Soaps seem to be the most effective of the controls available, but just a periodic shower is almost as effective.

Here is a link that might be useful: About Spider Mites

Thanks for the replies. It is a 50$ kratom tree, so I'm concerned about killing it in the transplanting process. I feel like pulling it out and rinsing the roots may cause serious damage and kill it.

Is transplanting it in sterile soil my only solution for the centipedes?

Also, I have been spraying the spidermites with habanero spray. Do you think insecticidal soap would be a good investment? Is there any sure fire way to stop them? Also, how do people stop them when their plants are much larger and they can't possibly spray every leaf?

Habanero, hot pepper, sprays are a deterrent not an insecticide while the insecticidal Soap is an insecticide.
As indicated in the link above Spider Mites can be difficult to control, but the lower the humidity around the plant the more you will have since higher humidity causes them to produce more.

This post was edited by kimmsr on Sat, Nov 16, 13 at 6:33

Interesting.

From Wiki centipede article:
" Centipedes are found in an array of terrestrial habitats from tropical rainforests to deserts. Within these habitats, centipedes require a moist micro-habitat because they lack the waxy cuticle of insects and arachnids, and so lose water rapidly through the skin."

Doubtful the soil of your plant is also housing enough critters to sustain centipedes, though possible. I wonder if they just find it a convenient place to stay when not hunting? If that is the case, repotting may or may not help if they are generally in the building and just hanging out in the pot. Keeping the soil less moist should make the pot a less habitable environment. Elevating the pot so air reaches the drain holes well (and are a bit harder to find if you're a bug crawling around on the floor could also help, if the pot is sitting on the floor (an assumption that a $50 tree is that big?)

Some centipedes do eat organic matter, so if excess moisture is causing roots to rot, that could be attracting them as well.

SM's are usually on the bottom of leaves, so any spray should be aimed there as much as possible. Are the leaves of this plant smooth (without hairs?) If so, wiping them with a cotton ball that is damp (not dripping) with rubbing alcohol can remove them. SM's can also be rinsed, if it's warm enough to take it outside and hose it down. If the soil/root ball is not 'shifty,' you can also lay it on its' side and do that in the shower. Try to avoid getting the soil soppy wet, I usually put the pot at the other end from the drain.

For plants that get SM's while inside, it's usually an ongoing battle to keep them at bay until plants can go back outside. They can show up from nowhere, so prophylactic systemic treatment before bring in does not ensure your plants will not get SM's later.

I suspect that the critters in question are millipedes rather than centipedes. The former are much more likely to take refuge in a potted plant, where it can feed on whatever the potting medium is composed of, as well as tender plant roots. Millipedes could also reproduce in a container.

Is that a possibility, agar?

Spider mites are a serious challenge for growers of indoor plants. The indoor climate is quite suitable for their rapid, unchecked, multiplication. General, occasional misting will not help.....unless the spray is directed to the underside of the leaves.

The types of showers suggested by purple can be helpful, however, but kind of an inconvenience. I often suggest misting with an alcohol solution, but you would need to do some testing first.

Have you tried placing the container in a larger watertight vessel of some kind, then flooding the plant in order to chase all of the critters out of the pot? You'll need to use enough water to truly flood your plant. This is a tried and true method used when people haul their plants back inside after a summer outside.

I'm not familiar with this plant other than reading about its legal status and questionable safety when consumed.
I can't help but doubt that it can be grown inside for very long unless you have greenhouse type conditions.

I assume that you are consuming the leaves, is that correct? If so, you can't use a systemic pesticide of any kind.

Spider mites prefer cool, dry conditions. Mildly soapy water sprayed on the leaves and allowed to dry will kill most of the adults and hatched young. Do this once or twice. Make sure to get the undersides of the leaves.
(Make sure to use organic soap.)
Repeat five days later to kill hatching eggs.
Shower plant between treatments or at the first sign of reappearance c warm water.
Spider mites hate water.
PS: Always isolate any houseplant to avoid spread to other plants.

"Spider mites reproduce rapidly in hot weather and commonly become numerous in June through September. If the temperature and food supplies are favorable, a generation can be completed in less than a week (Figure 5). Spider mites prefer hot, dusty conditions and usually are first found on trees or plants adjacent to dusty roadways or at margins of gardens. Plants under water stress also are highly susceptible. As foliage quality declines on heavily infested plants, female mites catch wind currents and disperse to other plants. High mite populations may undergo a rapid decline in late summer when predators overtake them, host plant conditions become unfavorable, and the weather turns cooler as well as following rain."

From the link I posted above, from the University of California.

predatory mites are your best bet, I grow lots of these trees. Transplanting is no problem. If you can harden the plant off slowly and get it outside, natural pests and condition will eiliminate the bugs. although, they may come back when you bring the plant indoors in fall, after a couple of months. If you are lucky, you will also bring in some of the natural predatory mites from outdoors too, which will keep the bugs in check

an yes, it is a plant used by people for thousands of years before our agency of Big Pharma profit protection was even thought of.