Lateral Dispersal and Foraging Behavior of Entomopathogenic Nematodes in the Absence and Presence of Mobile and Non-Mobile Hosts

Abstract

Entomopathogenic nematodes have been classified into cruisers (active searchers) and ambushers (sit and wait foragers). However, little is known about their dispersal and foraging behavior at population level in soil. We studied lateral dispersal of the ambush foraging Steinernema carpocapsae (ALL strain) and cruise foraging Heterorhabditis bacteriophora (GPS11 strain) from infected host cadavers in microcosms (0.05 m2) containing Wooster silt-loam soil (Oxyaquic fragiudalf) and vegetation in the presence or absence of non-mobile and mobile hosts. Results showed that the presence of a non-mobile host (Galleria mellonella larva in a wire mesh cage) enhanced H. bacteriophora dispersal for up to 24 hr compared with no-host treatment, but had no impact on S. carpocapsae dispersal. In contrast, presence of a mobile host (G. mellonella larvae) increased dispersal of S. carpocapsae compared with no host treatment, but had no effect on H. bacteriophora dispersal. Also H. bacteriophora was better at infecting non-mobile than mobile hosts released into the microcosms and S. carpocapsae was better at infecting mobile than non-mobile hosts, thus affirming the established cruiser-ambusher theory. However, results also revealed that a large proportion of infective juveniles (IJs) of both species stayed near (≤ 3.8 cm) the source cadaver (88-96% S. carpocapsae; 67–79% H. bacteriophora), and the proportion of IJs reaching the farthest distance (11.4 cm) was significantly higher for S. carpocapsae (1.4%) than H. bacteriophora (0.4%) in the presence of mobile hosts. S. carpocapsae also had higher average population displacement than H. bacteriophora in the presence of both the non-mobile (5.07 vs. 3.6 cm/day) and mobile (8.06 vs. 5.3 cm/day) hosts. We conclude that the two species differ in their dispersal and foraging behavior at the population level and this behavior is affected by both the presence and absence of hosts and by their mobility.

Mechanisms of host seeking by parasitic nematodes

“…Some ambushing Steinernema species also jump, where the IJ stands on its tail, curls, and propels itself into the air [6]. In general, ambushers are most effective at targeting motile hosts, while cruisers are most effective at targeting non-motile hosts [7]. However, recent studies suggest that many species are capable of engaging in either ambushing or cruising depending on the environmental context.…”

“…The extent to which Ste. carpocapsae moves in the soil also depends on which insect hosts are present [7, 9]. In addition, all EPN species examined so far exhibit robust chemotaxis in the presence of insect-derived odorants [10, 11].…”

Traits of the entomopathogenic nematode, Heterorhabditis bacteriophora (Hb-EG strain), for potential biocontrol in strawberry fields

“…Likewise, various biotic and abiotic factors can affect movement behavior (Perony and Townsend, 2013) such as group size (Bonnell et al 2013), environmental spatial structure and resource availability (Reeve and Cronin 2010), avoidance of predators (Beauchamp, 2017) and genetic diversity (Johnson et al 2016). Bal and Grewal (2015) found that the cruise foraging H. bacteriophora differ in its dispersal and foraging behavior from ambush foraging S. carpocapsae at the population level, and this behavior is affected by both the presence and absence of hosts and by their mobility. Ruan et al (2018) reported that EPN dispersal continuously exhibited an aggregative pattern (independent movement was not observed).…”

Entomopathogenic Nematodes Combined with Adjuvants Presents a New Potential Biological Control Method for Managing the Wheat Stem Sawfly, Cephus cinctus (Hymenoptera: Cephidae)

“…To minimize variation in WSS densities [21], plots were arranged linearly approximately equal distances from the edges of the fields. Individual plots were spaced ~8.0 m apart to avoid effects from overspray or migration of EPNs and plot order was randomized at each location [37]. …”