Natural predators are used more often these days as a biological method to combat insect plagues.
These pest control methods are primarily used for prevention.

The predators should be used with a certain regularity, even if insects are few in number.

This is especially true when controlling spider mites.
These predators can be ordered
from your local hydroponics shop.

They are delivered by mail and must be collected from the shop on the day they arrive - to prevent them all dying.