Many species of slugs are considered serious pests in agriculture and horticulture around the world. In Europe, slugs of the genera
Arion
and
Deroceras
are the most harmful pests in agriculture. ...Therefore, the main goal of this study was to evaluate the effect of the whole-cell metabolites of 10 strains of five
Xenorhabdus
and three slug-parasitic nematodes (
Phasmarhabditis hermaphrodita
,
Phasmarhabditis bohemica
, and
Phasmarhabditis apuliae
) on the feeding behaviour and repellent effect on target slugs and evaluate a new possible means of biocontrol of these pests. The repellent and anti-feedant effects of nematode-killed insects, metabolites, slug-parasitic nematodes and a combination of metabolites and nematodes were studied through experimental designs: sand-filled plastic boxes divided into two parts in several modifications: with dead
Galleria mellonella
killed by nematodes, lettuce treated with bacterial metabolites and lettuce placed on the treated sand. We found that slugs avoid eating
G. mellonella
killed by nematodes, while they eat freeze-killed
G. mellonella
. Similarly, they avoid the consumption of lettuce in areas treated with bacterial metabolites (the most effective strains being
Xenorhabus bovienii
NFUST,
Xenorhabdus kozodoii
SLOV and JEGOR) with zero feeding in the treated side. All three
Phasmarhabditis
species also provided a significant anti-feedant/repellent effect. Our study is the first to show the repellent and anti-feedant effects of metabolites of
Xenorhabdus
bacteria against
Arion vulgaris
, and the results suggest that these substances have great potential for biocontrol. Our study is also the first to demonstrate the repellent effect of
P. apuliae
and
P. bohemica
.
Key points
• Slugs avoid eating G. mellonella killed by entomopathogenic nematodes.
• Bacterial metabolites have a strong repellent and antifeedant effect on slugs.
• Presence of slug parasitic nematodes increases the repellent effect of metabolites.
Nematodes in the genus
can infect and kill slugs and snails, which are important agricultural pests. This useful trait has been commercialized by the corporation BASF after they mass produced a ...product labeled Nemaslug®. The product contains
, which has been cultured with
, a bacterial strain that was originally thought to be responsible for causing mortality in slugs and snails. The exact mechanism leading to death in a
infected host is unknown but may involve contributions from nematode-associated bacteria. The naturally occurring microbial community of
is unexplored; the previous
microbial community studies have focused on laboratory grown or commercially reared nematodes, and in order to obtain a deeper understanding of the parasite and its host interactions, it is crucial to characterize the natural microbial communities associated with this organism in the wild. We sampled
,
, and
directly from their habitats in Central and Southern California nurseries and garden centers and identified their native microbial community
16S amplicon sequencing. We found that the
microbial community was influenced by species, location, and possibly gastropod host from which the nematode was collected. The predominant bacteria of the
isolates collected included
,
, Aeromonadaceae, Pseudomonadaceae, and
.
isolates exhibited an enrichment with species belonging to Acinetobacter or Pseudomonadaceae. However, further research must be performed to determine if this is due to the location of isolate collection or a species specific microbial community pattern. More work on the natural microbial community of
is needed to determine the role of bacteria in nematode virulence.
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•Arion vulgaris had a high prevalence of endoparasites compared to native gastropods.•Arion vulgaris had a higher natural nematode load than Arion fasciatus.•Arion vulgaris tolerated ...infection by Phasmarhabditis hermaphrodita.•Arianta arbustorum displayed feeding inhibition and avoided nematode infested soil.•Invasive success of Arion vulgaris is possibly due to parasite tolerance.
The invasive slug Arion vulgaris (Gastropoda: Arionidae) is an agricultural pest and serious nuisance in gardens of Central and Northern Europe. To investigate if the success of A.vulgaris in Norway can be attributed to a release from parasites, we compared the prevalence and parasite load of nematodes and trematodes in A. vulgaris to that of three native gastropod species, A. circumscriptus, A. fasciatus and Arianta arbustorum, in SE Norway. We found A. vulgaris to have the highest prevalence of both parasite groups (49% nematodes, 76% trematodes), which does not support the parasite release hypothesis, but rather points to A. vulgaris as a potentially important intermediate host of these parasites. For trematodes the number of individuals (parasite load) did not differ among host species; for nematodes it was higher in A. vulgaris than A. fasciatus. To further compare the parasite susceptibility of the surveyed gastropods, we exposed A. vulgaris, A. fasciatus, and A. arbustorum to a slug parasitic nematode, Phasmarhabditis hermaphrodita, in the laboratory. This nematode is commercially available and widely used to control A. vulgaris. The non-target species A. fasciatus was most affected, with 100% infection, 60% mortality and significant feeding inhibition. A. vulgaris was also 100% infected, but suffered only 20% mortality and little feeding inhibition. The load of P. hermaphrodita in infected specimens was not significantly different for the two Arion species (median: 22.5 and 45, respectively). Only 35% of A. arbustorum snails were infected, none died, and parasite load was very low (median: 2). However, they showed a near complete feeding inhibition at highest nematode dose, and avoided nematode-infested soil. Our results indicate that A. vulgaris may be less susceptible to P. hermaphrodita than the native A. fasciatus, and that non-target effects of applying this nematode in fields and gardens should be further investigated.
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•T. elata larval survival outcomes depend on prey slug species.•Successful pupariation in T. elata is reduced for larvae fed on nematode-exposed slugs.•90% of T. elata neonate larvae ...without prey for four days pupariate successfully.•Neonate and third instar larvae appear to prioritise different predatory strategies.
While the larval stage of Tetanocera elata (Diptera: Sciomyzidae) is a known parasitoid and predator of pestiferous slugs, its biology and predatory behavior as well as its interaction with slug parasitic nematodes requires further investigation. In this study, survival of larvae fed from the neonate stage on Deroceras reticulatum Müller (a previously known prey species) was significantly greater (P = 0.023) than for larvae fed on Deroceras invadens Reise with 100% and 40% survival respectively. However, when fed solely on D. reticulatum which were previously exposed to P. hermaphrodita, only 20% of neonate larvae pupariated successfully. Ninety percent of neonate larvae maintained without food for the first four days and subsequently fed on D. reticulatum pupariated successfully although this decreased to below 50% for ≥6 days without food. Predatory third instar T. elata larvae appeared to select nematode-exposed D. reticulatum over non-exposed slugs with the continued feeding on nematode-exposed slugs also reducing the chances of successful pupariation by 25%. Records of maximum egg-laying by laboratory-reared female adults were greater (487 eggs) than previously recorded for field-caught adults (3 7 3). The implications of these results for the potential use of T. elata as a biological control agent of pestiferous slugs are discussed.
Performs a phylogenetic analysis of nematode mitochondrial DNA (mtDNA) strains representing eight different Phasmarhabditis species, collected from nine countries around the world, in order to ...identify the origin of species recently discovered in New Zealand and the western USA. Confirms that nematodes deriving from the Nemaslug® biocontrol product have invaded countries where its use as a biological control agent is prohibited by regulatory agencies and is not commercially available. Source: National Library of New Zealand Te Puna Matauranga o Aotearoa, licensed by the Department of Internal Affairs for re-use under the Creative Commons Attribution 3.0 New Zealand Licence.
Slugs and snails are agricultural pests usually controlled by chemical bait pellets however an alternative method is the commercially produced malacopathogenic nematode Phasmarhabditis hermaphrodita, ...which is sold across northern Europe. P. hermaphrodita can kill several slug species but is unable to affect larger pestiferous snails. Therefore, we examined whether the closely related species Phasmarhabditis californica, isolated from the U.K. could kill neonate or adult common garden snails (Cornu aspersum). In our first experiment, neonate C. aspersum were exposed to 1000 nematodes per tube containing three strains of P. californica (designated DMG0017, DMG0018 or DMG0019) (as well as the commercial formulation of P. hermaphrodita DMG0001) and feeding inhibition and survival were monitored over 14 days. All nematodes apart from P. californica (DMG0017) killed the snails and caused feeding inhibition. In a follow up experiment we exposed adult C. aspersum to two doses (30 and 90 nematodes per cm
2
) of P. californica (DMG0019) and P. hermaphrodita (DMG0001) and monitored survival, feeding inhibition and changes in weight over 21 days. Neither nematode species affected survival, feeding inhibition or weight of the adult snails. In summary, P. californica (DMG0018 and DMG0019) are as pathogenic as P. hermaphrodita (DMG0001) and could be used to target neonate snails, however, the use of malacopathogenic nematodes to control large adult snails continues to be problematic.
The nematode Phasmarhabditis hermaphrodita is lethal to a wide range of pest gastropod species. In Europe, it is available as a biocontrol agent (Nemaslug®), but its complete host range is yet to be ...determined. Our data showed that a U.S. strain of this nematode is lethal to the introduced, non-pest, subterranean slug, Testacella haliotidea, which substantiates the broad host range of P. hermaphrodita. These data highlight the need for completing additional testing with both pest and particularly native gastropod species before a decision is made on the use of P. hermaphrodita as a biocontrol agent in the U.S.
Phasmarhabditis hermaphrodita is a parasitic nematode of terrestrial gastropods that has been formulated into a successful biological control agent used on farms and gardens across Europe. There are ...reports of members of the Phasmarhabditis genus affecting the survival of non-target organisms under lab conditions e.g. earthworms. Therefore, we exposed two species of earthworm (Lumbricus terrestris and Eisenia hortensis) and insect (Galleria mellonella and Tenebrio molitor) to a range of doses of P. californica (0, 30 and 150 nematodes per cm2). P. californica did not affect earthworm or insect survival emphasising these nematodes are gastropod parasites that pose no risk to earthworms or insects (based on laboratory trials).
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