You might try setting up yellow sticky traps (found in garden centers), away from children or pets. These are usually used more for monitoring than control, but in an indoor environment, including a greenhouse, it can be more effective to control the adults, which are attracted to the color and get stuck. Also, if you have any houseplants that are infested with whiteflies, be sure to check the leaves regularly, and remove any older leaves that are severely infested with the larvae and pupae. Look for tiny oval eggs on leaf undersides. Wingless nymphs look sort of like pale scale insects, flattened and oval, and do not move after the first instar. Keep handpicking and controlling with the traps, and you might be able to overcome a mild infestation. Make sure that the insects are not easily coming in from the outside, or coming in on infected plants taken in from outdoors.
You might try setting up yellow sticky traps (found in garden centers), away from children or pets. These are usually used more for monitoring than control, but in an indoor environment, including a greenhouse, it can be more effective to control the adults, which are attracted to the color and get stuck. Also, if you have any houseplants that are infested with whiteflies, be sure to check the leaves regularly, and remove any older leaves that are severely infested with the larvae and pupae. Look for tiny oval eggs on leaf undersides. Wingless nymphs look sort of like pale scale insects, flattened and oval, and do not move after the first instar. Keep handpicking and controlling with the traps, and you might be able to overcome a mild infestation. Make sure that the insects are not easily coming in from the outside, or coming in on infected plants taken in from outdoors.