Influence of nitrogen fertility, surfactants, thatch and the availability of host insects on infectivity and persistence of the entomopathogenic nematode Heterorhabditis bacteriophora Poinar.

The turfgrass industry in the United States has grown at a rapid rate over the past half century, as large tracts of land have been developed to support the ever-growing suburban population. At the same time, public perception of potential negative health risks and environmental impacts associated with pesticides has prompted legislative restrictions on insecticide use. These concerns have motivated many turfgrass managers to consider alternative, non-pesticide management techniques or strategies that are aligned with integrated pest management (IPM). Entomopathogenic nematodes (EPN\u27s) possess characteristics that make them desirable biological alternatives to chemical insecticides. Unfortunately, factors affecting the ability of these nematodes to persist in the environment at levels sufficient to regulate insect pests are not completely understood. In order to move beyond the use of short-term inundative release techniques for these nematodes, a greater understanding of the factors influencing nematode establishment and persistence is needed. This thesis focuses on the impact turf inputs (nitrogen fertility and soil surfactants) and environmental conditions (thatch and availability of host insects) have on entomopathogenic nematode EPN persistence and infectivity and further examines the compatibility of these nematodes with various soil surfactants. In a growth chamber experiment, Nitrogen fertility, a soil surfactant and thatch significantly increased nematode persistence and both surfactant and thatch increased nematode infectivity. Additionally, laboratory assay results suggest that nematodes suspended in surfactant solution may persist longer than in water alone. Results of this research encourage the development of IPM programs that integrate entomopathogenic nematodes with certain common turfgrass management inputs (surfactants and N-fertility) and cultural practices (thatch management and conservation of alternate hosts) that may enhance the well-being and effectiveness of EPN\u27s. Findings could also improve the adoption of EPN\u27s in turfgrass pest management by allowing managers to move from costly inundative use of EPN\u27s toward more sustainable and cost effective inoculative approaches