Spatial patterns of entomopathogenic nematodes in microcosms: implications for laboratory experiments.

Area of Science:

• Entomology
• Nematology
• Soil Ecology

Background:

• Steinernema riobravis are entomopathogenic nematodes crucial for biological pest control.
• Understanding their survival in laboratory settings is vital for developing effective application strategies.
• Previous studies have not fully elucidated the impact of soil moisture and container effects on nematode survival in microcosms.

Purpose of the Study:

• To quantify the impact of soil moisture on the survival of Steinernema riobravis.
• To evaluate the suitability of laboratory microcosms for studying nematode motility and survival.
• To investigate nematode behavior, such as geotropism and migration, within different microcosm setups.

Main Methods:

• Laboratory microcosms (petri dishes and centrifuge tubes) were used to assess nematode survival.
• Soil moisture levels were varied to determine optimal conditions for S. riobravis.
• Nematode recovery methods included rinsing from surfaces and processing via Baermann trays.
• Negative geotropism and migration patterns were observed and quantified.

Main Results:

• Nematode survival in soil was significantly higher at 2-4% soil moisture compared to lower or higher levels.
• >95% decline in nematodes within soil in petri dishes over 7 days, with a 35-fold increase on dish surfaces.
• Nematodes exhibited negative geotropism, migrating towards container lids.
• Downward migration was inversely related to soil column diameter, suggesting surface-facilitated movement.

Conclusions:

• Laboratory microcosms can be adapted to study nematode survival, but container surface effects must be considered.
• Optimal soil moisture for S. riobravis survival in microcosms is between 2-4%.
• Moisture deficits may induce quiescence, potentially enhancing nematode survival in soil.