I was using a spray of 1T(tablespoon)Hemp oil, 1T hemp-peppermint castille soap, 1T H202, 1T 90% Isopropyl alcohol to a half gallon of warm water. I sprayed every 5 days 3 times and it was very effective for adults but had to keep spraying to catch the newly hatched. I had one that was ready for harvest but had a couple of visible adults as well as a few eggs. I did not want to spray just before harvest, and I did not want them to just keep eating my buds in the jar.
I remembered using CO2 to kill Drosophila (fruit flies) in a Genetics lab...
Now this wont work for everyone...but if you brew beer, use CO2 in your grow, or play paintball etc and have access to C02...you can kill them with the gas, while giving your plant a little spa treatment. The plant looked dramatically better afterward...think of it like a hyperbaric chamber like they use for wound healing using pure 02, but for plants!
This plant was ready for harvest so I just bent over the branches to fit in a black trash bag, sucked out air with vacuum, and stuck the hose from my CO2 bottle in the bag and filled it up...I secured the bag around hose with tape (later when doing multiple plants I twisted and tied the bags). I gave a couple of shots of gas over the next day or so and the buds looked healed and the mites were gone.
Note: I had always kept ladybugs for prevention until about Oct.
This worked so well for the plant ready for harvest, I stopped the spray regime, bought some 45 gallon clear bags from smart & final (to not disturb light cycle) and bagged up half the garden (It is small) gassed for 24hrs and then the other half. I then released about 300 lady bugs to clean up the mess and any that...might have held their breath for a day
I believe this also killed the eggs through osmosis or some gas law or something...cuz they looked dessicated and have not returned.
Note: the gas comes out pretty cold. The last two bags I filled, I filled the last right after filling the 1st, and though I had a plastic fitting preventing the gas from spraying directly on the plants...I gave the plants in the last bag a touch of frost bite...luckily these were in veg and in no hurry and have since started to recover.
Also When treating multiple plants in this manor, one should be aware of the toxicity of CO2 to people and animals as well as it's tendency to drop to the floor and resist exhaust...so be careful especially for little ones who crawl the floor...fuzzy or not.
I failed to re-up on ladybugs a few months back for their refusal to eat thrips (horticultural grade diatomaceous earth for all crawling larval stage pests!!!! sprinkle on soil surface)...I will never do that again, they are my friends!