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Effects of entomopathogenic nematodes on nutrient cycling, soil respiration and pistachio root growth

Hodson, A. K., J. P. Siegel and E.E. Lewis . 2010.

Abstract

Entomopathogenic nematodes (EPNs) can be used in pistachio orchards to control pest populations of navel orangeworm. When applied in large numbers, they may affect ecosystem processes as they emerge from hosts and release nutrients and bacterial exudates into the soil. We examined how EPNs affect nutrient availability, soil respiration (measured as CO2 efflux) and root growth in greenhouse microcosms. We compared treatments of bare soil, EPNs alone, nuts with EPNs, and nuts without applied EPNs. We also compared the effect of navel orangeworm infested pistachios with and without EPNs. EPNs had no effect on N bioavailabilty or root growth either when applied alone or with navel orangeworm larvae. EPNs did cause significant reductions in navel orangeworm numbers compared to controls. While EPNs did not affect CO2 efflux, respiration in nuts-only treatments was significantly higher than treatments with no nuts. Higher levels of respiration were also observed in those treatments containing navel orangeworm larvae. In complex systems containing microorganisms, soil arthropods and growing plants, EPNs seem to have little effect on nutrient cycling, soil respiration and root growth.

Key Words

Nitrogen supply; entomopathogenic nematodes; non-target effects; nitrogen cycling; soil respiration; root growth.