Chapter 5
Biology
Abstract
The life cycle of the entomopathogenic nematodes Steinernema and Heterorhabditis consists of two phases
namely a free-living phase in the soil and a parasitic phase inside the insect host. Steinernema IJs use
ambusher strategy and Heterorhabditis IJs use cruiser strategy to locate their insect host. IJs enter the insect
host through natural openings like mouth, anus and spiracles or cuticle. The metabolites produced by
bacteria are lethal to the larvae and the host insect is killed by septicemia or toxemia. The bacterial
metabolites have a wide-spectrum of antimicrobial activity. Biocontrol potential of EPNs depends on the
mutualism amongst a host-seeking nematode and a lethal insect-pathogenic bacterium.
Keywords Life cycle, Infective juveniles, Host, Septicemia, Metabolites, Biocontrol
l
Three special features of Steinernema and Heterorhabditis nematodes present them as an amazing study platform in biocontrol
purposes.
l
First, they form a complex nematode–bacterium mutualistic
symbiosis. The nematodes carry the bacteria in their body and
release them into the insect hosts [40].
l
Second, they are insect pathogens with a very wide host range
that covers most of the insect orders.
l
Third, they can be mass produced either in vivo or in vitro.
l
Although the two nematode groups show similarity in infecting,
killing, and emerging as a new generation from insect hosts, they
exhibit difference in their life cycles [93].
l
The life process of the nematode–bacteria complex explains the
mode of action of these potent biological insecticides.
S. Sivaramakrishnan and M. Razia, Entomopathogenic Nematodes and Their Symbiotic Bacteria, Springer Protocols Handbooks,
https://doi.org/10.1007/978-1-0716-1445-7_5,
© The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature 2021
19
Biology
Abstract
The life cycle of the entomopathogenic nematodes Steinernema and Heterorhabditis consists of two phases
namely a free-living phase in the soil and a parasitic phase inside the insect host. Steinernema IJs use
ambusher strategy and Heterorhabditis IJs use cruiser strategy to locate their insect host. IJs enter the insect
host through natural openings like mouth, anus and spiracles or cuticle. The metabolites produced by
bacteria are lethal to the larvae and the host insect is killed by septicemia or toxemia. The bacterial
metabolites have a wide-spectrum of antimicrobial activity. Biocontrol potential of EPNs depends on the
mutualism amongst a host-seeking nematode and a lethal insect-pathogenic bacterium.
Keywords Life cycle, Infective juveniles, Host, Septicemia, Metabolites, Biocontrol
l
Three special features of Steinernema and Heterorhabditis nematodes present them as an amazing study platform in biocontrol
purposes.
l
First, they form a complex nematode–bacterium mutualistic
symbiosis. The nematodes carry the bacteria in their body and
release them into the insect hosts [40].
l
Second, they are insect pathogens with a very wide host range
that covers most of the insect orders.
l
Third, they can be mass produced either in vivo or in vitro.
l
Although the two nematode groups show similarity in infecting,
killing, and emerging as a new generation from insect hosts, they
exhibit difference in their life cycles [93].
l
The life process of the nematode–bacteria complex explains the
mode of action of these potent biological insecticides.
S. Sivaramakrishnan and M. Razia, Entomopathogenic Nematodes and Their Symbiotic Bacteria, Springer Protocols Handbooks,
https://doi.org/10.1007/978-1-0716-1445-7_5,
© The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature 2021
19