I used Neem oil before, mixed with dish soap and a little rubbing alcohol. Never had much luck. Bayer 3 in 1 was best but they changed the formula and Bonide is still great. From what I heard, it's no use on mites. Sevin is and walmarts always has it on sale cheap. I use Sevin before bring all my plants in for winter and again in early summer. I use the liquid Sevin and it does leave a white residue behind but it washes off easily. (which I don't do).
It has killed Aloe mite for me and that's one of the hardest ones to control.
There is a leaf disease called Anthracnose of Sansevieria which is said there is no cure. For that I have used original Listerine mouthwash. It contains all the stuff to kill bacteria and fungus. Mixed in a spray bottle about half and half and then I add a spoonful of Baking Soda. Helps. Some time the main plant dies but it produces new pups and they seem okay.
When buying new plants, it is best not to mix in with your existing collection for several months. Reason summer is best time to buy and experiment.
