It is important to understand that pest control, no matter the method, does not mean pest annihilation. In nature, balance equals control. In your garden, control equals a successful integrated pest management program. The use of beneficial insects is one step towards successful control.
The first step for any form of pest control is to identify the culprit and decide if the level of damage actually warrants control. Also, you don't want to mistake a good bug for a bad one.
Springtime is the best time to begin using beneficial insects. Aphids, especially, are attracted to the tender, succulent new growth. Their nemesis is the ladybeetle, which can be purchased by the bag or box containing from 1,500 per pint to 70,000 per gallon. The best way to release them is to dampen the foliage with water and gently shake them on the base of the plant at dusk. The idea is to dampen their wings so they can't fly away, although your neighbors would appreciate it if they did.
Green lacewings are the most versatile because they control a variety of pests including, aphids, caterpillars, spider mites, thrips, among others. It is possible to establish a natural population of them through a series of releases throughout the spring and summer.
Trichogramma wasps go for tomato hornworms, cabbageworms, and many orchard pests. They come on cards or in small containers that you attach directly to the plant. They are miniscule gnat-like parasitic wasps and should also be applied in a series of releases.
The praying mantis will eat almost any pest including grasshoppers, flies, caterpillars, beetles and roaches. They come in egg cases containing approximately 200 eggs. They are not great hunters and generally wait for their prey to happen along, but I think their dramatic value outweighs their bad habits. Note: Don't be like my sister and let them hatch out in the house.
Beneficial insects are available from your local nursery or you can order directly from an insectary, a place for growing beneficial bugs, many listings of which are available on the Internet. Receiving an order from the insectary takes about ten days but results in a greater number of live insects that actually make it to your garden. The insectary can recommend what type of beneficial insects your garden needs as well as application instructions.
The cost of treating your garden to a helping of beneficial bugs ranges from roughly $8 per bag of lady beetles to $22.00 for a case of lacewings. It is interesting to note that some insectaries have reported a growth rate of nearly 20 to 25 percent per year. A clear indication that more gardeners are opting for less toxic methods of pest control.