well, im not much of an expert on much of anything else, but this one is something i know something about.....A spider mites favorite form of transportation is dust. The problem can become very pronounced in agricultural areas. Do you live in the sticks? A car driving by can send enough dust through your house to cause the problem. Open windows, vent systems....just about any open system in your house can let them in. The best insecticide to use on them is a weak solution of Kelthane....its the same stuff you put in your cats ears for ear mites. Dont use the stuff after your buds are on ,but anytime before that is ok