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Moisture Effects on Entomopathogenic Nematodes 1998

Project Leaders: Jennifer Grant, Michael Villani

Objectives:

1. Determine the infectivity and reactivation capacity of entomopathogenic nematodes under varying soil moisture levels in the laboratory.

2. Determine the infectivity and persistence of entomopathogenic nematodes in the field, under soil conditions manipulated to vary in moisture levels.

Results:

Our previous work showed that entomopathogenic nematodes were able to survive dry soil conditions, and did not infect insects while maintained at these low soil moistures. We were able to activate the nematodes by raising the soil moisture as long as 9 weeks after inoculation. This year both Heterorhabditis bacteriophora (Hb) strains in the driest soil (6% moisture) rebounded to 100% infection levels throughout a 10-month period. Results were similar in the 9% soil, though insect mortality rebounded to a slightly lower level. Steinernema glaseri (SG) nematodes did not recover as well as either of the Hb strains, and had the highest rebound in the 9% soil. This implies that SG was less able to tolerate very dry conditions.