Another quick answer from the brewman -
I hope people don't think I'm a loser for posting on damn near every thread today. I'm at work and bored.
3 things. water soap peppers. If your cacti are old enough and in pots ( i wouldn't try this on seedlings ) you can try drowning them. Get a tub deeper than your cactus is tall and fill to the top with water. Drop cactus in and wait 30min - 1hour. I've done this several times and it never hurt my little green babies. I'm also assuming you want to avoid harsh chemicals and insecticides.
You can also use dish soap diluted with tap water to 2%-5%. Spray on. Just avoid getting alot of soap in the soil. They also make "pesticidal soaps" that contain potasium salt of fatty acids. These work by breaking down the waxy coating on the mites and they die by losing all their stored water. Die mites Die!!!!
Last, get yourself a habanero pepper or two and cut them open. If you've never had any experience with a habanero be careful, they're deadly ( 1000 times hotter than a jalapeno ) wear gloves. And for god sakes don't put any in your eye. Rub the insides of the pepper all over the cactus in between the spines getting juice all over it. All insects hate this shit. I do this once a month while my cacti are outside in the summer. I also use it to keep ants off my counter top in the spring. Good luck. I hope this helps.
