This weekend, I finally got around to dealing with the Greenhouse whitefly infestation we've had on the basil and mint in the kitchen window. We've previously tried Pyrethrin-based insecticides, but eventually the whiteflies came back.
After a bit of research, it appears that insecticide resistance is a fairly common occurrence with whiteflies, and other alternative approaches are needed to manage the infestation. In our case, since the plants are relatively small, I opted for drowning the plants for a few moments, and then putting yellow sticky traps out. Hopefully this will at least let the basil come back and keep the whiteflies under wraps.