To hellp with a whitefly problem in the greenhouse?
1)Try some Encarsia formosa, a biological control agent
2) Safers soap works great and is non-toxic
3)In drastic cases, get a nicotine or similar "bomb",
seal the greehouse and wipe out all the insects (not
my first choice, but it beats losing all your plant
4) With few plants, you can dip them in a mild soap (not Detergent)
solution and run off allthe bugs.