This is the best control for flying insect pests that I found...
Using sticky traps! I use the specific one called Safer Brand Houseplant Stick Stakes. They control whitefly, blackfly, thrips, fungus gnats, fruit flies, midges, and most other flying insects. You can usually buy this specific trap at Earl May or at:
Amazon.com: House Plant Sticky Stake 7 Pack: Patio, Lawn & Garden
I've used them and they work very well. I keep a few sticky stakes around my plants continuously.
Let me know if these work for you...