Many studies of entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) have reported that only a small
proportion (typically <40%) of infective stages (dauers), even under apparently ideal conditions, actually infect a host.
The ‘phased infectivity hypothesis’ is most frequently invoked to explain this pattern of low infection with
entomopathogenic nematodes. It proposes that at a given point in time not all individuals are infectious i.e. infectiousness is delayed
in some individuals. We tested experimentally several predictions based on this hypothesis. Specifically, if phased
infectivity occurs, we should be able to expose dauers to increasing numbers of potential hosts until dauers no longer infect
and still be able to recover viable dauers. These recovered dauers which did not infect should be infectious at some later
point in time. However, our results do not support the phased infectivity hypothesis for 3 species of Steinernema: most
dauers could be recovered in one sampling round when provided with sufficient suitable hosts. In contrast, Heterorhabditis
bacteriophora frequently did not infect all available hosts, and infectious dauers were recovered in subsequent sampling
rounds. This result is more consistent with the phased infectivity hypothesis, but further research is needed before we can
be more confident in the hypothesis. For all species tested, the number of available hosts influenced population levels of
nematode infectivity. This suggests that the infection status of hosts can influence whether a dauer infects. Our results
indicate that phased infectivity is not a common phenomenon in entomopathogenic nematode dauers, despite the
widespread acceptance of this hypothesis.