Try the dry ice method that I posted about a couple of months ago; there is some criticism about the drop in temperature. If you do the method correctly, the temp drop will not be that drastic. Just remember to put the container of water and dry ice on a trivet of some sort to keep it from chilling the receptacle. If it does get cool, just remove the container/fog maker and 'pour' the CO2 fog in until all the air is gone. Once you put the top on you can sit it in the (indirect) sun or another warm place to bring the temp up a little if needed, but I never have needed to do so.
This method will smother all oxygen breathing organisms and will give a boost to the plant. This is very good for scale and mealies as it get's down in the cracks.
You can get dry ice here at Walmart or at an ice cream shop. Hope this helps!
Steve