This is a good article about using methods other then poisonous sprays to control insect pests.
Here is a link that might be useful: Eco friendly garden pest control
To start, many entomologists discourage purchasing lady beetles -- may be one of the reasons the native populations are declining.
It is not just entomologists that discourage purchasing the Lady Beetles, but many environmentalists also do since many of those selling them collect the Lady Beetles from the wild depleting the populations in that area.
The major reason why the Lady Beetle population declining is most likely the amount of insect poisons being sprayed as well as habitat destruction.
& even from just an efficiency standpoint lady bird Beatles are not worth it. They are horrible at controlling aphids when compared to other biocontrol.
Introduce aphiduis Spp. or Aphidoletes aphidimyza.