IncredibowlBoss
Member
This site http://pubs.acs.org/doi/abs/10.1021/jf00054a045 touts CO2 extraction
The research I've seen recommends essential oils - not extracts; usually essential oils are made by crushing the plant material and squeezing the oils out of it, rather than any extraction process. Essential oils have a relatively higher terpenoid content - terpenoids are what make the oil smell, it also turns out that it's the terpenoid compounds that are deadly to mites.
Gotta try lavender, but rosemary works fantastically (kills adults, juveniles, and eggs) - laboratory tests indicate that Eucalyptus and peppermint are up to 30% more deadly to the little fuckers. That leads me to believe that tea tree (melaleuca) oil would be similarly effective (you can smell the similarity in the terpenoids between these oils - there's a certain minty-ness to them all).
Grad thesis on spider mite control with essential oils: http://www.miresmalli.com/resources/Thesis-final.pdf