Hi aimster - these white flies are a nuisance. Are they indoors or out? I think you have the same as we had a while back - but not sure - anyhow will try my best here .......
We had problems with them few years back - re house plants. We must have brought back a plant (have quite a few in the house) that was infested - and it took off from there.
As I won't use pesticides - I repotted every plant, washed the leaves, stems down etc - made sure the pots were clean etc. It took a while - but touch wood - we got rid of the little critters. Hope this is of some help. :o)