There is an often-referenced but under-implemented army of spineless mercenaries wandering our nurseries in search of glory and fame.
Ok, that might be a bit melodramatic, but it’s not necessarily untrue. Natural enemies – that is, the natural enemies of PEST insects – are a naturally occurring force for good in production systems, feeding on every stage of many of our most economically important pests. Just as the pest insects invade when we supply an abundance of leafy hosts, the natural enemies of those pests respond to the abundance of prey. However, waiting and hoping these beneficial insects appear in sufficient numbers to manage a pest outbreak doesn’t always seem like a safe bet, which is why methods for enhancing the efficacy of natural enemies have become a staple in Integrated pest management strategies.
Utilizing natural enemies in crops has become increasingly popular as more species are available for mass releases from commercial suppliers – everything from the predatory mites that feed on the eggs and young of soft-bodied insects and other mites, to the above-pictured green lacewing, the juveniles of which not only appear as a tiny alligator, but feed just as voraciously (image right).
Understanding both the pest and the natural enemies in your system is key to utilizing the natural enemies as a pest management resources. It’s important to target all stages of the pest insect, which means identify the natural enemies that attack the different stages and encouraging the natural enemy populations at the right time. There are three main strategies for encouraging natural enemies:
- Conservation. Conserving the natural enemies that already exist in the production zone includes providing habitat and alternate food resources, so that when they prey numbers decline, the natural enemies don’t leave the area. This could mean providing debris for overwintering or alternate host plants that will not only attract pest *away* from crops but give predators a continual food resource.
- Augmentation. Once you’ve identified the natural enemies in your system, you can temporarily boost the population size by augmenting with commercially available NEs to create more pressure on the pest population. This can be used to target adults during mating season to limit reproductive success, or used to target egg and juvenile stages to limit damage later in the season. Understanding pest biology will help make decisions on how and when to use this strategy. Combined with conservation strategies, this can provide long term suppression, potentially lasting more than a single season.
- Inundation. This strategy is similar to augmentation but is usually implemented in artificial settings, such as greenhouses, when natural enemy populations are usually low or non-existent. Introducing a natural enemy at a high density to control a pest population can provide rapid suppression, though in this strategy, it usually is less reasonable to expect the natural enemies to remain once pest numbers are low. This is usually implemented with the expectation that natural enemies will need to be reintroduced as need.
Of these strategies, augmentation is the most ideal place to start – harnessing the natural enemies already occurring in your production zone. In 2021, the Nackley Lab released the pocket guide to Common Natural Enemies in Nursery Crops and Garden Pests (image right, click to download) to aid in identification and to help with decision-making when it comes to using natural enemies in pest management strategies. With color images showing distinguishing characteristics, commonly mistaken species and information on scouting for these natural enemies, it can help you get started with natural enemies in your crop.