I'll give you my OPINION, as you can ask 100 people and everyone has a different solution. I fought mites for many years, and used just about every product on the market at one time or another. There are many threads here on RIU about fighting mites and you might want to check them out too. Most anything sprayed on plants while flowering will have a negative effect on plants and maybe your health. As you probably know it's always better to try and eliminate the issue before flowering. But you have to be careful in flowering, especially with "oil-based" or citrus products as most will kill back the bud stigma's. Here's my specific recommendation:
Buy a product called PurCrop1. It's sold at MonsterGardens. It's expensive, but you only need 2-4 tablespoons per gallon for a spraying. It's oil based but developed under a different process that won't harm your plants if applied properly. You can find a lot about it under a google search. Spray when the room and plants are cool and well watered. Shake the sprayer often to keep everything mixed, and spray like your life depends on it. Spray everything, inclusing pots, walls and flooring. It's more important to spray UNDER the leaves and along stems rather than the above canopy. If you need to turn lights on, wait 1-2 hours until everything is dry. Turns fans off too, let it all dry naturally. If you already have a problem, and are in flowering- apply at the 1 fluid oz (2 tablespoons) per gallon.
In veg, I use the 2 fluid oz per gallon rate until bud start to form, then reduce down to 1 fluid oz in flowering. I like to spray in the morning, after a thorough watering the day before and the room is at it's coolest point. I spray weekly, if you have an issue, you can spray a couple of times a week.
Lastly, do not spray one product on top of another (on top of another). Most will interact in a negative way with each other, but not all. Thoroughly research it first.
