Whitefly sit on the undersides of CBD leaves and lift off in a cloud when the plant is disturbed, which is how people first notice them. They suck sap, leave sticky residue and sooty mould, and the eggs hatch in waves so a single treatment never clears them. Yellow sticky traps hung at canopy height plus repeated soap sprays a few days apart are the routine described on https://calmcbdseeds.com by growers in greenhouses, where whitefly are worst. Encarsia wasps finish the job if you can get them.
