Entomopathogenic nematodes and their symbiotic bacteria: from genes to field uses

Abstract

The term “microbial control” has been used to describe the use of microbial pathogens (bacteria, viruses, or fungi) or entomopathogenic nematodes (EPNs) to control various insect pest populations. EPNs are among the best biocontrol agents, and major developments in their use have occurred in recent decades, with many surveys having been conducted all over the world to identify EPNs that may have potential in the management of insect pests. For nematodes, the term “entomopathogenic” means “causing disease to insects” and is mainly used in reference to the bacterial symbionts of Steinernema and Heterorhabditis (Xenorhabdus and Photorhabdus, respectively), which cause EPN infectivity. A compendium of our multiannual experiences on EPN surveys and on their collection, identification, characterization, and use in agro-forestry ecosystems is presented here to testify and demonstrate once again that biological control with EPNs is possible and offers many advantages over chemicals, such as end-user safety, minimal damage to natural enemies, and lack of environmental pollution, which are essential conditions for an advanced IPM strategy.

Identification and biocontrol potential of entomopathogenic nematodes, Steinernema siamkayai occurring in western Thailand against the common cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) under laboratory and screenhouse conditions

“…In this study, the three S. siamkayai isolates were collected from undisturbed areas near waterfalls, and no Heterorhabditis nematodes were detected. Similar results indicated that Steinernema nematodes were recovered twice as frequently as Heterorhabditis nematodes during EPN survey in Italy (Tarasco et al, 2015(Tarasco et al, , 2023. It has been noted that Steinernema nematodes are more abundant in terrestrial environments, while Heterorhabditis nematodes are commonly found in coastal sites (Hominick, 2002;Tarasco et al, 2015).…”

“…However, some publications have reported that Heterorhabditis nematodes were recovered 2-4 times more frequently than Steinernema nematodes (Aryal et al, 2022;Kour et al, 2020;Malan et al, 2006;Noosidum et al, 2010). The diversity and occurrence of EPN are influenced by soil-related factors, both abiotic and biotic factors in vegetative environments (Aryal et al, 2022;Susurluk & Ehlers, 2008;Tarasco et al, 2015Tarasco et al, , 2023, as well as EPN seasonal dynamics (Půža & Mráček, 2005).…”

“…Generally, EPN distribution can be highly aggregated, and a small sample size may reduce the chances of EPN recovery (Hazir et al, 2003). Several previous studies have indicated varying rates of successful EPN recovery, ranging from 2 to 45% in soil samples obtained from different environments (Hominick, 2002;Tarasco et al, 2015Tarasco et al, , 2023. Surveys in specific habitats with a higher prevalence of EPN generally achieve a greater recovery compared to non-targeted surveys (Mráček & Bečvář, 2000).…”