Best thing for spider mites or aphids is AVID miticide by SynGen. Expensive but extrmely effective.
I lost my patience and money getting rid of mites on my very very large Black Magic. Tried
all kinds of insecticide labeled for mite, nothing, they seemed to thrive on the stuff.
One application with AVID and it was like a theromuclear attack, gone, zip, nada left of the Mites.
AVID will not harm plants specifically Black Magic which is very tender foliage.
I have Nancy's Revenge, Mojito, Pink China, Black Magic, Hydrax, alocasia Nile High and Esculenta and
about 50 Caladiums.
None have ever shown any aphids or Spider Mites on them. Let them beware my new Nuclear arsenal
will wipe them out. This stuff is incledible [a bit expensive] but well worth it.