The problem with the Bayer type sprays, or systemics is that bees and butterflies will die if they go to any of the plants' flowers. The systemics will last in the plants' system for a year. We need to do what we can to keep their populations healthy.
We had a massive problem with white fly last year in Florida. I used the soapy water solution also. Here's the recipe, recommended by our county Ag agent.
2-1/2 tbsp of cooking oil, plus 2-1/2 tbsp of baby shampoo. Mix in one gallon of water.
You do need to wash it off within a few hours. Spray ever 5-7 days as needed. This also good for mealy bugs. When I saw the eggs on the undersides of the leaves, I also just hosed them off, as the eggs wouldn't be viable on the ground.
Something else that does work, is using yellow plastic plates smeared in Vaseline. The flies are attracted to yellow. I hang them near my tomato plants. just make a hole in the plate's rim and thread string through and find something to hang it from. When the plate gets yucky with the bad bugs, and it will, just make up a new one.
