A century of advancement in entomopathogenic nematode formulation and application technology

Entomopathogenic nematodes (EPNs) in the genera Heterorhabditis and Steinernema are biocontrol agents used to control a diverse array of economically important insect pests. Generally, nematodes are applied in aqueous suspensions using standard agricultural equipment (e.g., sprayers and irrigation systems). Formulation and application parameters are critical to the level of biocontrol efficacy achieved by EPNs. Moreover, biocontrol efficacy is mitigated by various abiotic and biotic factors. For example, abiotic factors such as ultraviolet (UV) radiation, desiccation, or temperature extremes can severely limit EPN efficacy in biocontrol. Additionally, biotic aspects, including matching the appropriate EPN species to the target pest, and a suitable application rate, are of extreme importance. EPN formulations can facilitate storage and ease-of-handling during application. Improved formulations may also protect the EPNs from harmful environmental conditions and enhance efficacy and persistence. For example, protective gels or nanoparticle formulations can protect nematodes from UV and desiccation and thereby expand EPN use to aboveground applications. Novel application approaches can also enhance EPN efficacy such as using pheromone boosters to increase nematode movement and infectivity. In this review, we summarize the current status of EPN formulation and application technology and provide examples of novel developments that will help propel EPNs toward future success. Following a brief introduction on current formulation and application practices, we provide information on the basic abiotic and biotic factors that affect efficacy, followed by approaches to improve efficacy within the framework of formulation and application technology.