In a search for an entomopathogenic nematode to control cranberry insect pests, three Oscheius populations (Rhabditidae) were recovered through the Galleria-bait method from one sample taken in a wild cranberry marsh in Jackson County, Wisconsin, USA. Morphological studies with light microscopy and scanning electron microscopy, as well as molecular analyses of the near-full-length small subunit rDNA gene, D2/D3 expansion segments of the large subunit rDNA gene, internal transcribed spacer, and mitochondrial cytochrome oxidase subunit 1 (CoxI) genes revealed this as Oscheius onirici, a species recently described from a karst cave soil of central Italy. The species belongs to the dolichura-group and is characterized by its DNA sequences; hermaphroditic reproduction; and males not found. A Bacillus-like bacterium appears to be associated with this nematode based on our microscopic and SEM observations; however its identity and persistent association with the nematode has not been confirmed. Nonetheless, this nematode is capable of infecting and killing the sparganothis fruitworm Sparganothis sulfureana Clemens (Lepidoptera: Tortricidae), the brown-banded cockroach Supella longipalpa Fabricius (Blattodea: Ectobiidae), and the cranberry fruitworm Acrobasis vaccinii Riley (Lepidoptera: Pyralidae), under laboratory conditions, and each in less than 72 hr. The mealworm Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae) and the greater wax moth Galleria mellonella Linnaeus (Lepidoptera: Pyralidae), are also susceptible, but take 3.5 and 5.2 days to die, respectively. This species is a new potential bio-control agent on insects.

The processes by which organic life is consumed and reborn in a complex ecosystem were investigated through a multiomics approach applied to the tripartite Xenorhabdus bacterium- Steinernema nematode- Galleria insect symbiosis. Trophic analyses demonstrate the primary consumers of the insect are the bacteria, and the nematode in turn consumes the bacteria.

The spotted-wing drosophila, Drosophila suzukii Matsumura, is an exotic species in North America and represents a major threat to fruit production. Efforts to manage D. suzukii have focused primarily on insecticides, but such controls may, at times, be unreliable, given that D. suzukii larvae are often ensconced within fruit. The fruit interior, however, may represent suitable foraging substrates for carnivorous/entomopathogenic nematodes. In preliminary trials, a rare nematode species, Oscheius onirici Torrini et al., was shown to be highly virulent against D. suzukii when the nematodes were applied directly to fly larvae. To address the more important question of whether this nematode would be as virulent when applied to fruit, we set up assays in which blueberries were infested with D. suzukii larvae and then sprayed with O. onirici infective juveniles (IJs). Across two laboratory trials, O. onirici IJs suppressed D. suzukii puparia by 78.2%. Oscheius onirici IJs were able to search effectively within fruit substrates, find the fly larvae therein, and kill the flies before they could pupariate. Oscheius onirici, therefore, may represent a viable new bio-control agent for D. suzukii management and should be field-tested across a broader diversity of cropping systems.

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Microbial symbiotic interactions, mediated in part by small molecule signaling, drive physiological processes of higher order systems, including the acquisition and consumption of nutrients that support symbiotic partner reproduction. Advances in metabolic analytic technologies provide new avenues to examine how chemical ecology, or the conversion of existing biomass to new forms, changes over a symbiotic lifecycle. Here we examine such processes using the tripartite relationship involving the nematode host Steinernema carpocapsae, its obligate mutualist bacterium, Xenorhabdus nematophila, and the insects they infect together. The nematode infective juveniles infect insects into which they release bacteria that help suppress insect immunity and kill the insect. The nematode-bacterium pair consume the insect cadaver and reproduce until nutrients are depleted, causing a new generation of infective juvenile nematodes, colonized by the bacterial symbiont, to leave the cadaver in search of insect prey. To begin to understand the processes by which insect biomass is converted over time to either nematode or bacterium biomass, we took a three-pronged approach integrating information from trophic, metabolomics, and gene regulation analyses. Trophic analysis established bacteria as the primary insect consumers, with nematodes at a trophic position of 4.37, indicating consumption of bacteria and likely also other nematodes. Metabolic changes associated with bioconversion of Galleria mellonella insects were assessed using multivariate statistical analyses of metabolomics datasets derived from sampling over an infection time course. Statistically significant, discrete phases were distinguishable from each other, indicating the insect chemical environment changes reproducibly during bioconversion. Tricarboxylic acid (TCA) cycle components and amino acids such as proline and leucine were significantly affected throughout the infection. Hierarchical clustering revealed a similar molecular abundance fluctuation pattern for nucleic acid, amino acid, and lipid biosynthesis metabolites. Together, these findings contribute to an ongoing understanding of how symbiont associations shape chemical environments.

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