Biological pest control in greenhouse crops is usually based on periodical releases of mass-produced natural enemies, and this method has been successfully applied for decades. However, in some cases there are shortcomings in pest control efficacy, which often can be attributed to the poor establishment of natural enemies. Their establishment and population numbers can be enhanced by providing additional resources, such as alternative food, prey, hosts, oviposition sites or shelters. Furthermore, natural enemy efficacy can be enhanced by using volatiles, adapting the greenhouse climate, avoiding pesticide side-effects and minimizing disrupting food web complexities. The special case of high value crops in a protected greenhouse environment offers tremendous opportunities to design and manage the system in ways that increase crop resilience to pest infestations. While we have outlined opportunities and tools to develop such systems, this review also identifies knowledge gaps, where additional research is needed to optimize these tools.

In the banker plant method, long-lasting rearing units for beneficials are created in the crop by distributing plants infested with herbivores or carrying other food items, such as pollen. The method has been widely investigated over many years and used to aid establishment, development and dispersal of beneficial organisms employed in biological control. In this review, we refine the definition of the banker plant method based on previous concepts and studies and offer the term “banker plant system” to describe the unit that is purposefully added to or established in a crop for control of pests in greenhouses or open field. The three basic elements of a banker plant system (banker plant, food source, beneficials) are discussed and illustrated with examples, and the diversity of banker plant systems (classified by target pest) used or investigated is documented. The benefits of using banker plant systems, such as low cost, increased freshness of beneficials, possibility for preventive control and for integration within IPM frameworks, make the method an interesting plant protection option with potential to enhance adoption of biological control in pest management programs.