We've had very similar experience to George Karlin-Neumann with Orthene,
Resmethrin and the Safer soaps. The organophosphates are rough on fresh
crosses, in particular. For persistent infestations or with especially
sensitive plants, we sometimes quarantine a growth chamber, spray it as
much as the plants will support, then completely eliminate the insects with
several sprayings when all plants have been discarded. Not so easy for
greenhouses, I imagine. Good luck, Andrew Millar.