I have not had to deal with thhis one yet....so I copied this off of MynameStitch's thread over at IC---any credit should be to him. Personally, if it were me, seeings how your 3 wks from harvest, I 'd try the insecticidal soaps and mix in some Neem(35%) to give it more staying power, smothering ability. They shouldn't be too bad in the buds themselves so dont soak them and risk residual tastes or mold.....but most definately keep on your newest clones! After a day or two I 'd kind of rinse off the Neem with more soap....then a few days before harvest rinse again w/h2o.<----try to do these rinses before your lights come on so the majority of sprays have dried(ventilate).
By, MynameStitch:
"you can use insecticidal soap, this will help stop them from flying so it wont infect other plants.
It also stops them from laying new eggs. If you use the soap reapply weekly.
If insecticidal soap does not work too well, there is some other options that are stronger called PERMETHRIN dust, Which can be used during flowering and is safe on ediable plants.
Here are some other good things to use to rid of white flys: PERMETHRIN and biffen (both are safe to use on ediable plants),
Spreader sticker ( hich allows to apply the spray to a wider area)
Nylar ( works well for inhibiting there growth and development)ORTHENE FOGGERS works well for a small area and are safe on the plants.Other poducts you can try are:
Hot Pepper Wax,Safer Yard & Garden Insecticide (which can be used right to the day of harvest),GNATROL( used in hydro in the water as well as soil),Doc's Neem Pest Soap,Safer Sticky Stakes,TR-11000 Pyrethrum."
Good Luck!!
growinman