Oviposition by the fungus gnat Bradysia impatiens (Diptera: Sciaridae) on geranium plants (Pelargonium x hortorum) inoculated with microorganisms

Dark-winged fungus gnats in the genus Bradysia (Diptera: Sciaridae) are ubiquitous greenhouse pests. Studies have pointed to a connection between plant disease outbreaks and fungus gnats, and it is generally thought that these pests vector a broad range of plant pathogens. However, despite the great importance of root rot pathogens in greenhouse crops, little research has been done on oomycete-fungus gnat associations. As part of a research program on the interactions among B. impatiens, Pythium spp., and floral crops, the objective of this study was to determine if inoculating geranium plants with various microorganisms would increase their attractiveness to female fungus gnats, measured in terms of oviposition. In laboratory experiments, fungus gnats exhibited a strong preference for ovipositing on plants associated with a wide variety of microorganisms, including pathogenic and non-pathogenic Pythium spp., fungi, and bacteria. Our findings correlate well with other studies that have reported increased fungus gnat survival in the presence of abundant growth of fungi and other microbes. These experiments enhance our understanding of basic fungus gnat behavior and interactions among fungus gnats, microorganisms, and floral crops important in the greenhouse setting.