EFFECTS OF SOIL-TEMPERATURE, MOISTURE, AND RELATIVE-HUMIDITY ON ENTOMOPATHOGENIC NEMATODE PERSISTENCE

Soil temperature, moisture, and relative humidity (RH) effects on the survival and pathogenicity of Steinernema carpocapsae and S. glaseri were tested in the laboratory. Survival and pathogenicity of S. carpocapsae were significantly greater at lower temperatures (5-25°C) than at the highest temperature (35°C). Conversely, S. glaseri survival and pathogenicity were significantly greater at higher temperatures (15-35°C) than at the lowest temperature (5°C). S. carpocapsae and S. glaseri survived best at low soil moistures of 2 and 4%, respectively. After rehydration by bringing up all tested moistures to 16%, both nematode species caused lethal infection of Galleria mellonella larvae. Survival and pathogenicity of these two nematode species decreased as RH decreased from 100 to 25% over the 32-day test period. At 100% RH, S. carpocapsae and S. glaseri survived for 32 days, but as RH was lowered, survival decreased. For example, at 25% RH, S. carpocapsae survived for 2 days and S. glaseri survived for only 4 hr. Pathogenicity was reinitiated after rehydration and showed a trend similar to survival. These differences in survival and pathogenicity may be attributed to the climatic origins or the soil habitats of these two nematode species. © 1991.