[Edited_by_A._Ciancio,_C.N.R.,_Bari,_Italy_and_K.(Bookos.org)

IPM THROUGH ENTOMOPARASITES
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In addition, some opportunistic, free living nematodes are capable of entering
insect cadavers and appropriating the nutients produced by the EPN-bacteria
symbiosis to the extent that the EPNs fail to reproduce (Duncan et al., 2003; 2007).
Some species of EPNs appear to be especially susceptible to this competitive
displacement by free living species but, again, the significance of these interactions
on EPN population dynamics is unknown. Clearly, much remains to be done to
understand how food web components interact to affect EPN patterns in space and
time.
Figure 4. Cuticle of Steinernema diaprepesi heavily encumbered by spores of
Paenibacillus sp., a non-pathogenic bacterium that reproduces within insects killed by
the nematode and its entomopathogenic symbiont, Xenorhabdus doucetiae. Movement
through soil by infective juvenile nematodes is impeded by heavy infestations of
Paenibacillus sp. Scale bar: 10 µm.
3.2. Identifying Factors that Regulate EPN Abundance and Efficacy
As noted previously, spatial surveys have revealed numerous relationships between
EPN prevalence and various soil physical properties such as porosity (texture), water
potential, chemistry, as well as cropping and management history. If causality can be
demonstrated then some of these relationships have the potential to be exploited to
develop cultural practices that enhance biological control. For example, some types of
soil mulches have significantly enhanced populations of EPNs (Bednarek & Gaugler,
1997; Duncan et al., 2007) whereas others appear to have no or negative effects on
EPNs (Lacey, Arthurs, Unruh, Headrick, & Fritts, 2006). Bednarek and Gaugler