Mortality of the invasive white garden snail Theba pisana exposed to three US isolates of Phasmarhabditis spp (P. hermaphrodita, P. californica, and P. papillosa).

Theba pisana is a serious snail pest in many parts of the world and affects diverse crops including grain, vegetables, grapevines, and ornamental plants and shrubs. Due to its gregarious nature, ability to reproduce rapidly, and the difficulty of controlling it by conventional methods, it has the potential to become a significant pest where introduced. Mitigating this pest is an important challenge that must be addressed. Phasmarhabditis hermaphrodita, is a gastropod-killing nematode that is commercially available only in Europe (Nemaslug ®) and Sub-Saharan Africa (Slugtech ® SP). The use of effective gastropod-killing nematodes in the genus Phasmarhabditis (P. hermaphrodita, P. californica and P. papillosa) in California may provide one strategy for alleviating the potential damage and further spread of these snails, which are currently limited to San Diego and Los Angeles counties. Laboratory assays demonstrated for the first time that US isolates of P. hermaphrodita, P. californica and P. papillosa at 150 DJs/cm2 caused significant mortality and are equally lethal to T. pisana. Molluscicidal efficacy of these nematodes are comparable with those of iron phosphate, at the recommended high dose of 4.88 kg/m2. Additional trials are needed to determine their effects at lower dose and whether they are dependent on the size or age of the snails

Baujardia mirabilis gen. n., sp n. from pitcher plants and its phylogenetic position within Panagrolaimidae (Nematoda: Rhabditida).

Summary -Measurements, line drawings and scanning electromicrographsare provided of Baujardia mirabilis gen. n., sp. n., isolated from pitcher uid of Nepenthes mirabilis from Thailand. The new genus differs from all known nematodes in having two opposing and offset spermatheca-like pouches at the junction of oviduct and uterus. It also differs from most known Rhabditida in having four cephalic setae instead of papillae. Phylogenetic analysis of small subunit rDNA sequence data robustly places the new genus within Panagrolaimidae as a sister taxon to Panagrellus. These unusual nematodes resemble Panagrellus in body size (1.8-2.7 mm in females, 1.3-1.9 mm in males) and in the monodelphic, prodelphic female reproductive system with thickened vaginal walls and prominent postvulval sac. However, they differ from Panagrellus in the characters mentioned above, in their comparatively longer stegostom and in the shape of the male spicules. Because of its aberrant characters, inclusion of this new genus in Panagrolaimidae requires changes to the family diagnosis

Baujardia mirabilis gen. n., sp. n. from pitcher plants and its phylogenetic position within Panagrolaimidae (Nematoda: Rhabditida)

Summary -Measurements, line drawings and scanning electromicrographsare provided of Baujardia mirabilis gen. n., sp. n., isolated from pitcher uid of Nepenthes mirabilis from Thailand. The new genus differs from all known nematodes in having two opposing and offset spermatheca-like pouches at the junction of oviduct and uterus. It also differs from most known Rhabditida in having four cephalic setae instead of papillae. Phylogenetic analysis of small subunit rDNA sequence data robustly places the new genus within Panagrolaimidae as a sister taxon to Panagrellus. These unusual nematodes resemble Panagrellus in body size (1.8-2.7 mm in females, 1.3-1.9 mm in males) and in the monodelphic, prodelphic female reproductive system with thickened vaginal walls and prominent postvulval sac. However, they differ from Panagrellus in the characters mentioned above, in their comparatively longer stegostom and in the shape of the male spicules. Because of its aberrant characters, inclusion of this new genus in Panagrolaimidae requires changes to the family diagnosis

Pellioditis pelhamensis n. sp. (Nematoda: Rhabditidae) and Pellioditis pellio (Schneider, 1866), earthworm associates from different subclades within Pellioditis (syn. Phasmarhabditis Andrássy, 1976)

Recently, much attention has been focused on a group of rhabditid nematodes called Phasmarhabditis, a junior synonym of Pellioditis, as a promising source of biocontrol agents for invasive slugs. Pellioditis pelhamensis n. sp. was first isolated from earthworms near Pelham Bay Park in Bronx, New York, USA, in 1990 and has been found to be pathogenic to slugs as well as some earthworms. It has also been used in several comparative developmental studies. Here, we provide a description of this species, as well as a redescription of a similar earthworm-associated nematode, Pellioditis pellio Schneider, 1866, re-isolated from the type locality. Although P. pelhamensis n. sp. and P. pellio are morphologically similar, they are reproductively isolated. Molecular phylogenetic analysis places both species in a clade that includes all species previously described as Phasmarhabditis which are associated with gastropods. Phasmarhabditis Andrássy, 1976 is therefore a junior synonym of Pellioditis Dougherty, 1953. Also, Pellioditis bohemica Nermut’, Půža, Mekete & Mráček, 2017, described to be a facultative parasite of slugs, is found to be a junior synonym of Pellioditis pellio (Schneider, 1866), adding to evidence that P. pellio is associated with both slugs and earthworms. The earthworm-associated species P. pelhamensis n. sp. and P. pellio represent different subclades within Pellioditis, suggesting that Pellioditis species in general have a broader host range than just slugs. Because of this, caution is warranted in using these species as biological control agents until more is understood about their ecology

Nematode associates and susceptibility of a protected slug (Geomalacus maculosus) to four biocontrol nematodes

The impact of selected entomopathogenic nematodes and Phasmarhabditis hermaphrodita on the European-Union-protected slug Geomalacus maculosus and the sympatric Lehmannia marginata was investigated. There was no significant difference in mortality between slugs treated with nematodes and their controls. The presence of P. hermaphrodita in two G. maculosus cadavers may be the result of necromenic behaviour. This study constitutes the first record of P. californica in Europe

Phylogenetic evidence for the invasion of a commercialized European Phasmarhabditis hermaphrodita lineage into North America and New Zealand

Biological control (biocontrol) as a component of pest management strategies reduces reliance on synthetic chemicals, and seemingly offers a natural approach that minimizes environmental impact. However, introducing a new organism to new environments as a classical biocontrol agent can have broad and unanticipated biodiversity effects and conservation consequences. Nematodes are currently used in a variety of commercial biocontrol applications, including the use of Phasmarhabditis hermaphrodita as an agent targeting pest slug and snail species. This species was originally discovered in Germany, and is generally thought to have European origins. P. hermaphrodita is sold under the trade name Nemaslug®, and is available only in European markets. However, this nematode species was discovered in New Zealand and the western United States, though its specific origins remained unclear. In this study, we analyzed 45 nematode strains representing eight different Phasmarhabditis species, collected from nine countries around the world. A segment of nematode mitochondrial DNA (mtDNA) was sequenced and subjected to phylogenetic analyses. Our mtDNA phylogenies were overall consistent with previous analyses based on nuclear ribosomal RNA (rRNA) loci. The recently discovered P. hermaphrodita strains in New Zealand and the United States had mtDNA haplotypes nearly identical to that of Nemaslug®, and these were placed together in an intraspecific monophyletic clade with high support in maximum likelihood and Bayesian analyses. We also examined bacteria that co-cultured with the nematode strains isolated in Oregon, USA, by analyzing 16S rRNA sequences. Eight different bacterial genera were found to associate with these nematodes, though Moraxella osloensis, the bacteria species used in the Nemaslug® formulation, was not detected. This study provided evidence that nematodes deriving from the Nemaslug® biocontrol product have invaded countries where its use is prohibited by regulatory agencies and not commercially available

Impact of castor meal on root-knot and free-living nematodes

Soil amendment may enhance soil quality as well as reduce plant-parasitic nematode. Despite the many applications already undertaken using castor meal, its efficiency in controlling root-knot nematodes (RKN, Meloidogyne incognita) when applied to melon (Cucumis melo) is still not clear. Three different amounts of castor meal (Ricinus communis) applied were evaluated in microplots planted with melon either with or without RKN. The impact of castor meal on soil free-living nematode communities was also determined. Total nematode genera richness was estimated as 37 for the entire set of microplots sampled across both sampling dates. Rarefaction analysis resulted in 12 collector's curves out of the total of 30 that reached the horizontal asymptote. Univariate ANOVA with two factors yielded differences (p < 0.05) only with regard to the time factor. Simpson, Shannon, Evenness and Equitability indices showed a trend toward moderate increases by the end of the experiment, while the other indices were higher for tomato in pre-transplant sampling compared to harvest. Nematode community and diversity changed during the course of the experiment, although there was substantial confounding heterogeneity within and between the factorial combinations from the beginning. Root knot population was not reduced by the castor meal but increased throughout the period, regardless of treatment. RKN reduced melon yield, number and weight of melon

Dose dependence of Phasmarhabditis isolates (P. hermaphrodita, P. californica, P. papillosa) on the mortality of adult invasive white garden snails (Theba pisana).

Theba pisana is an invasive snail pest which has established itself in San Diego County and some areas of Los Angeles County, California. The snail has grown to large populations in some areas and mitigation is becoming necessary to stop the spread of the species. In a previous study, three US strains of Phasmarhabditis species (P. californica, P. papillosa, and P. hermaphrodita) effectively killed juvenile (0.25 gram each, 4-6 mm wide) T. pisana in laboratory conditions at 5 times (150 IJs/cm2) the recommended dose. Based on laboratory assays, we demonstrated that the same three US strains of Phasmarhabditis can effectively kill larger adult T. pisana (0.4-1.2 gram, 11.5-15mm wide) in two weeks at the same dose. The strains were more efficient at killing T. pisana than the compared molluscicide Sluggo Plus®. Results further showed that the most virulent P. californica did not effectively kill T. pisana at lower doses of 30 IJs/cm2 and 90 IJs/cm2. Additional research is needed to develop the most efficient means of application of Phasmarhabditis to mitigate T. pisana in the field