Biological control of terrestrial molluscs usingPhasmarhabditis hermaphrodita—progress and prospects

Abstract

Phasmarhabditis hermaphrodita Schneider (Nematoda: Rhabditidae) is a nematode that parasitises a wide range of slug and snail species. It has been formulated into a biological control agent (Nemaslug) and was commercialised in 1994. It is now available in fourteen European countries. A review is given of all research on P. hermaphrodita, including basic biology, mass cultivation, formulation, host range, application strategies, field efficacy and effects on non-target organisms. The many critical gaps in present knowledge are highlighted, and future research is proposed that will lead to greater understanding of this unusual parasite and may enable its more widespread use in the management of mollusc pests.

The effect of different growing substrates on the development and quality ofPhasmarhabditis hermaphrodita(Nematoda: Rhabditidae)

“…This observation suggests that, unlike EPNs (Yang et al, 1997), P. hermaphrodita can produce full quality DJs on a variety of substrates including plant tissue. This fact is in accordance with the saprobic lifestyle of P. hermaphrodita (MacMillan et al, 2009;Rae, Verdun, Grewal, Robertson, & Wilson, 2007).…”

Performance of the slug parasitic nematode <i>Phasmarhabditis hermaphrodita</i> under predicted conditions of winter warming

“…10) Our results also support previous findings by Wilson et al 9) about the optimum population growth temperature range of P. hermaphrodita, which is between 12 and 18°C, since in the WW plots, the mean daily minimum and maximum temperatures were 11.3°C and 16.2°C, respectively, within a range of extreme values of 10.1 and 18.5°C. In the NW plots, the mean daily minimum temperature was 6°C, with an extreme value of 2.2°C, and it has been shown that the reproduction of P. hermaphrodita decreases significantly below 10°C.…”

“…The significant interaction between climate treatment and nematode presence/ absence in both slug damage and slug numbers suggests that an increased mean winter temperature in the range of 4.0-4.5°C, as predicted for NW Spain, might improve the performance of P. hermaphrodita as a slug biocontrol agent during the winter. Early inhibition of slug feeding following infection by P. hermaphrodita is considered a key factor in the success and rapid action of the nematode as a biocontrol agent, 6,10) and this aspect of the interaction between P. hermaphrodita and D. reticulatum seems to have benefited from the winter warming conditions of the experiment: 3 days after the introduction of slugs into the trays, there were no differences between treatments in slug numbers, while slug damage was significantly lower in the nematode-treated plots under WW conditions than under NW conditions.…”

“…8) P. hermaphrodita is intolerant to moderately high temperatures 9) and very sensitive to desiccation and exposure to ultraviolet light when applied to the soil surface. 10) Thus, predicted climate changes in terms of increased temperatures are likely to have important effects on both D. reticulatum and its nematode parasite P. hermaphrodita as well as on their relationship. 9) Although the thermal ecology of P. hermaphrodita is poorly understood, Wilson et al 9) recently demonstrated that the nematode is much less tolerant of increasing temperatures than the host slug D. reticulatum, in the range of 14 to 24°C.…”

The slug parasitic nematode Phasmarhabditis hermaphrodita associates with complex and variable bacterial assemblages that do not affect its virulence

“…Another much less studied nematode that is sold throughout Europe as a biological control agent is the slug parasite, Phasmarhabditis hermaphrodita (Rae et al, 2007), under the tradename Nemaslug Ò . This nematode shares many similarities with entomopathogenic nematodes in that it forms dauer juveniles that infect slugs.…”