The Biochemical Adaptations of Spotted Wing Drosophila (Diptera: Drosophilidae) to Fresh Fruits Reduced Fructose Concentrations and Glutathione-S Transferase Activities.

Spotted wing drosophila, Drosophila suzukii Matsumura, is an invasive and economically damaging pest in Europe and North America. The females have a serrated ovipositor that enables them to infest almost all ripening small fruits. To understand the physiological and metabolic basis of spotted wing drosophila food preferences for healthy ripening fruits, we investigated the biological and biochemical characteristics of spotted wing drosophila and compared them with those of Drosophila melanogaster Meigen. We found that the susceptibility to oxidative stressors was significantly increased in spotted wing drosophila compared with those of D. melanogaster. In addition, we found that spotted wing drosophila had significantly reduced glutathione-S transferase (GST) activity and gene numbers. Furthermore, fructose concentrations found in spotted wing drosophila were significantly lower than those of D. melanogaster. Our data strongly suggest that the altered food preferences of spotted wing drosophila may stem from evolutionary adaptations to fresh foods accompanied by alterations in carbohydrate metabolism and GST activities.

Molecular analysis of a novel gene cluster encoding an insect toxin in plant-associated strains of Pseudomonas fluorescens.

Pseudomonas fluorescens CHA0 and the related strain Pf-5 are well-characterized representatives of rhizosphere bacteria that have the capacity to protect crop plants from fungal root diseases, mainly by releasing a variety of exoproducts that are toxic to plant pathogenic fungi. Here, we report that the two plant-beneficial pseudomonads also exhibit potent insecticidal activity. Anti-insect activity is linked to a novel genomic locus encoding a large protein toxin termed Fit (for P. fluorescensinsecticidal toxin) that is related to the insect toxin Mcf (Makes caterpillars floppy) of the entomopathogen Photorhabdus luminescens, a mutualist of insect-invading nematodes. When injected into the haemocoel, even low doses of P. fluorescens CHA0 or Pf-5 killed larvae of the tobacco hornworm Manduca sexta and the greater wax moth Galleria mellonella. In contrast, mutants of CHA0 or Pf-5 with deletions in the Fit toxin gene were significantly less virulent to the larvae. When expressed from an inducible promoter in a non-toxic Escherichia coli host, the Fit toxin gene was sufficient to render the bacterium toxic to both insect hosts. Our findings establish the Fit gene products of P. fluorescens CHA0 and Pf-5 as potent insect toxins that define previously unappreciated anti-insect properties of these plant-colonizing bacteria.

Susceptibility of the strawberry crown moth (Lepidoptera: Sesiidae) to entomopathogenic nematodes.

The objective of this study was to determine the susceptibility of the strawberry crown moth, Synanthedon bibionipennis (Boisduval) (Lepidoptera: Sesiidae) larvae to two species of entomopathogenic nematodes. The entomopathogenic nematodes Steinernema carpocapsae (Weiser) strain Agriotos and Heterorhabditis bacteriophora (Steiner) strain Oswego were evaluated in laboratory soil bioassays and the field. Both nematode species were highly infective in the laboratory bioassays. Last instars were extremely susceptible to nematode infection in the laboratory, even in the protected environment inside the strawberry (Fragaria x ananassa Duch.) crown. Infectivity in the laboratory was 96 and 94% for S. carpocapsae and H. bacteriophora, respectively. Field applications in late fall (October) were less effective with S. carpocapsae and H. bacteriophora, resulting in 51 and 33% infection, respectively. Larval mortality in the field from both nematode treatments was significantly greater than the control, but treatments were substantially less efficacious than in the laboratory. Soil temperature after nematode applications in the field (11 degrees C mean daily temperature) was below minimum establishment temperatures for both nematode species for a majority of the post-application period. It is clear from laboratory data that strawberry crown moth larvae are extremely susceptible to nematode infection. Improved control in the field is likely if nematode applications are made in late summer to early fall when larvae are present in the soil and soil temperatures are more favorable for nematode infection.

Persistence of Metarhizium anisopliae incorporated into soilless potting media for control of the black vine weevil, Otiorhynchus sulcatus in container-grown ornamentals.

The objective of this study was to determine the persistence of Metarhizium anisopliae (F52), measured as infectivity against black vine weevil larvae, in a soilless potting medium at six wholesale nursery locations across the Willamette Valley, Oregon. A granule formulation (0.30 and 0.60 kg/m(3)) was incorporated into media at planting and fungal persistence determined over two growing seasons. The fungus persisted in the potting media over the duration of the experiment with 50-60% of the larvae exposed to treated media becoming infected at the end of the experiment. The percentage of infected larvae gradually declined from > or = 90% on week 3 to 40-60% by week 19. Larval infection rebounded over the fall and winter months of 2004 to 75-80% followed again by a slow decline over the course of the second growing season.