Remember that all sprays are chemicals - bees and other insects can be killed by them. It follows that these bug-killers should be used sparingly, when you have an infestation on a plant.

Try washing them off with soapy water first, before using sprays.

Nurserymen used to recommend regular preventive spraying, until we found out how much damage we were doing to the environment that way. Now we recommend inspecting the plants regularly to catch infestations early, identifying exactly which pest is the problem, and using the most ecologically sound method of management you can. If there is a particular pest that comes back every year at the same time--such as borers or agave snout weevils here in the desert--preventive spraying may be indicated, but that isn't real common.

Don't spray with insecticides outside of the greenhouse at all.