I have just detected whitefly on several houseplants. I have Safer Entire Insect Killer for trees and shrubs, it mentions whitefly but says nothing about use on houseplants. Are there different "Safer's"? I hope I don't end up with an epidemic here, lots of plants in jeopardy. :_|

Yes, they have Safer's for houseplants. If you can't find it, try spraying them with a mild soap solution under leaves and on stem, then shake table salt on the plant as you hold it upside down. B-)

Look at the labels and if they have about the same mixture of soap what you have would be okay for the houseplants. I've not seen any diference in the 3 types of Safers I've looked at.
Put some yellow sticky traps around the house plants to trap the adults and distrub them as often as possible to get them flying onto the yellow sticky traps.
Do not put table salt on your house plants, or any plants.

That's what I'd have thought too, but a Mennonite friend does it. They even sprinkle salt on soap-sprayed cabbage as cabbageworm control.

I know if you sprinkle salt on the top of dew-dampened weeds, it acts as a natural herbicide. Go figure.

Basil keeps white fly away. It smells lovely but the fly hates it.
Good luck B-)