Biological control is a crucial tool for managing pests in organic crop production. Arthropod natural enemies provide significant ecosystem services that favor the suppression of agricultural insect pest populations. When you maintain permanent habitats and food sources for the natural enemies of pests in the vicinity of your farms, it favors the continuous availability of the natural enemies. When the growing season starts, the good bugs will be readily available to attack the pests before they become established in the crops. Planting a diversity of flowering plants (e.g., sweet alyssum, nasturtium, milkweeds, common cryptantha, hillside vervain, wild petunia, etc.) on a small portion of your farms or the farms border can provide adequate food and shelter allowing to maintain abundant and diverse natural enemy species, including syrphid flies, tachinid flies, lacewings, parasitic wasp, etc. that will attack aphids, thrips, lepidopterans, and more.  

Figure 1. Insectary plants planted in field margins to attract and conserve natural enemies.

Figure 2. Some suggested insectary plants. 

Intercropping, the practice of growing different crops in the same field, is also a suitable agricultural practice for managing insect pests because landscape diversity plays a crucial role in biodiversity conservation and sustainable pest management. Crops grown in intercropping systems are more likely to be less injured than those grown in monoculture. The non-host companion plants can have repellent or deterrent properties that act against insect pests that attack the main crop. Companion plants can also trap the pests, reduce their ability to locate the host plant, and increase the abundance of natural enemies. Like in a push-pull intercropping system, your main crop is intercropped with plant species that can make it less visible or can emit undesirable volatiles (smells) that divert the pests away from the main crop, on the other hand, other plants in your intercropping system can be extremely attractive using stimuli that are highly apparent and attractive to the pest, hence trapping the pest (Fig. 3). Insects use visual, chemical, or tactile cues to locate their host. Thus, by intercropping the main crop with plants that emit more attractive scents, which are more visually appealing, or can release undesirable odors to the pests, we can reduce the abundance and impact of the pest on the main crop.

Figure 3. Pictorial representation of push-pull strategy. 

In Brazil, the push-pull strategy has been found effective in managing major kale pests. They found that using mustard as a preferred host pulled the pests away from the kale crops, while marigold plants increased the beneficial arthropod population, which provided additional control of the pests. In Salinas, California, intercropping lettuce with sweet alyssum has favored some measurable aphid control. Sweet alyssum attracts and feeds hoverflies, which then lay eggs in lettuce, producing hoverfly larvae that consume aphids (Fig. 4).  

Figure 4. Graphical representation of Lettuce-Alyssum intercropping system for aphids
control. (Image source: Brannan 2013). 

As you plan for the next season, you can consider planting flowering plants along the borders of your farms or in dedicated patches to conserve natural enemies and enhance your biological control. When feasible, consider intercropping multiple crop species that are not affected by the same pests; this will reduce the abundance of insect pests and also increase the abundance and diversity of beneficial insects.