Behavioral ecology of entomopathogenic nematodes

Abstract

We discuss the behavior and ecology of entomopathogenic nematodes in relation to their successes and failures as biological control agents. Four categories of studies have been reviewed herein; infective juvenile foraging strategies, recognition and evaluation of the host by infective juveniles, the actual behaviors of infective juveniles that result in infection, and the protective role of the symbiotic bacteria during nematode reproduction in the cadaver. This constitutes a chronological order of events. Two challenges are suggested. First, the data on entomopathogenic nematode behavioral ecology, while very extensive for some species, are almost completely lacking for most described species. We need to approach future studies paying more attention to phylogenetic origins of the traits that we study. Second, there is little consensus on exactly what are the traits that are worth studying. By reviewing and synthesizing current work, we make some suggestions about where future research should be directed.

Movement of Heterorhabditis amazonensis and Steinernema arenarium in search of corn fall armyworm larvae in artificial conditions

“…Studies of these factors in species that were not studied previously are especially important. It would be incorrect to assume that phylogenetically related species necessarily exhibit the same behaviour patterns (Campbell et al, 2003;Lewis et al, 2006). The current study verified that H. amazonensis is capable of host search and of moving through the substrate for significant distances, finding the host at distances up to 60 cm, as for S. arenarium.…”

“…This enclosure was divided into five parts by placing pieces of Styrofoam at distances of 10, 20, 40, 60 and 80 cm from the opening ( Figures 1A and 1B). EntomopathoEntomopathogenic nematodes forage for their hosts in various ways and can exhibit cruiser or ambusher behavior (Lewis, 2002;Lewis et al, 2006;Stuart et al, 2006). In our experiments, the distance 80 cm length was chosen as the maximum initial distance between nematode and host, as was deemed sufficient to assess cruiser type foragers.…”

Sex ratios and sex-biased infection behaviour in the entomopathogenic nematode genus Steinernema

“…Grewal et al (1993) reported that male IJs of four species of Steinernema (Steinernema glaseri, Steinernema carpocapsae, Steinernema scapterisci and Steinernema anomali, but not Steinernema feltiae) disperse, locate and establish in distant live hosts before females, and proposed that males of these species are colonisers, invading the host before females and making the infected host more attractive to female IJs. This male colonisation hypothesis was not supported by a later study on S. glaseri (Stuart et al, 1998) and has remained controversial (Lewis et al, 2006). In contrast, Bohan and Hominick (1997) reported that female S. feltiae IJs invaded insect hosts before males, leading to a markedly femalebiased sex ratio during the initial phase of the infection, but the sex ratio became balanced as the infection progressed.…”

Behaviour and Population Dynamics of Entomopathogenic Nematodes Following Application

“…Once in the host's habitat, the parasite may again move randomly until it encounters the host's "active space" (area of the habitat modified by the presence of the host -gradients of CO 2 , other chemicals, temperature) after which more directed host-searching along gradients brings the parasite to the host surface (McInnis). For EPN, the host's active space will frequently be chemical in nature (Dillman et al, 2012;Lewis et al, 2006), though vibrations (Torr, Heritage, & Wilson, 2004) and fine-scale temperature gradients (Burman & Pye, 1980;Byers & Poinar, 1982) may also be effective components of the insect host active space.…”

“…There are already several extensive reviews relevant to the subject, including EPN behaviour and their fate in soil (e.g. Griffin, 2012;Kaya, 2002;Lewis, Campbell, Griffin, Kaya, & Peters, 2006;Stuart, Barbercheck, Grewal, Taylor, & Hoy, 2006;see also Chap. 4).…”