Ladybugs worked for me , they ate all day, and i had noticed physical signs of them being there, ie... webbing. The ladybugs will not fly away if there is a good eating envirment for them to habitat, this being advice from the greenhouse owner, ended up being true. but spraying before is a good idea, they are very thirsty when they awake from there hybernation, you dont want them flying off looking for water, put them at the base of the plant and have them work there way up..