Biological control is an important IPM tool globally. This pest suppression technique is especially important for managing pests in organic crop production. There are various biological control techniques, including conservation biological control, classical biological control, and augmentative biological control. Conservation biological control is the practice of providing habitat to support abundant populations of naturally occurring arthropods that attack crop pests. However, classical biological control and augmentative biological control involve the release of arthropod predators and parasitoids, usually non-native, into the field or greenhouses. This article focuses on conservation biological control.

The contribution of native beneficial insects to pest control has been estimated to be approximately $4.5 billion annually in the United States alone. However, the benefits of beneficial insects areoften overlooked. Research conducted across the country has shown evidence that conserving natural habitats leads to an increase in beneficial arthropod populations and a reduction in pest problems on farms. Beneficial arthropod predators and parasitoids often rely on natural or semi-natural areas adjacent to the field for their persistence. Between growing seasons, these natural and semi-natural areas provide alternative food sources, overwintering, and nesting habitats for natural enemies, thereby promoting their populations. To complete their life cycle, natural enemies require more than just prey or hosts; they also need refuge sites and alternative food sources.

Neighboring natural and semi-natural habitats serve as sources of natural enemies during the growing seasons to suppress crop pests. The establishment of wildflower margins around crop fields increases the abundance of beneficial insects that search for pollen and nectar. For example, many adult parasitoids sustain themselves with pollen and nectar from nearby flowering plants while searching for hosts. Most natural enemies do not disperse far from their overwintering sites; access to permanent habitat near or within the field gives them a jump-start on early pest populations.

Farms with diverse and dense populations of natural enemies are likely to exhibit the following characteristics:

- Have small fields surrounded by natural vegetation.
- Composed of diversified cropping systems and plant populations in or around fields include perennials and flowering plants.
- Crops are managed organically or with minimal agrichemicals.
- Soils are high in organic matter and biological activity and, during the off-season, covered with mulch or vegetation.

Figure 1. Syrphid fly feeding from sweet alyssum flowers.


Figure 2. Mix flowers planted on strips between rows of celery to provide food and
shelter for natural enemies.