Beneficial insects do a lot of pest management naturally, with little help from us. Lady beetles, syrphid fly larvae, and lacewing larvae eat soft-bodied pests like aphids and scale crawlers. Some parasitoid wasps lay eggs on aphids and the developing young wasps kill their aphid host. Minute pirate bugs eat thrips and aphids. These beneficial insects and others are part of the natural fauna of your farm.
Here is link to a great fact sheet from the University of Maine that shows what some of the most common beneficial insects look like —http://umaine.edu/publications/7150e.
I recently heard Carol Glenister of (Integrated Pest Management) IPM Laboratories talk about “Guardian” plants and how they can be used to enhance beneficial insect populations. This article summarizes some of the things I learned from her.
Many people are interested in having populations of beneficial insects inhabit their fields, high tunnels and greenhouses. One strategy is to purchase beneficial insects from a commercial supplier and release them. This is known as augmentation, and can be an effective way to manage pests. Keys to successful augmentation include properly identifying the pest, choosing a beneficial that is proven to be effective, having an adequate ratio of prey to beneficial, and following all the directions carefully. Even if you do all these things exactly right, there are no guarantees that augmentation will always work. There are so many variables that it is impossible to always get it exactly right.