Environmental Variables and Insect Pathology: Key Insights from Ecological Interactions in the Screening Experiment of Biocontrol Bacteria in the Larvae of the Songmo Longhorn Beetle

This study tested bacterial strains for biocontrol of Songmo longhorn beetle larvae and infesting pine wood nematodes. Experimental objective was to identify bacteria that are pathogenic to the larvae or to the nematodes within them. Pine wood nematode-parasitized larvae were collected, bacteria were recovered from dead larvae to be subjected to pathogenicity testing. Media were prepared by dissolving agar powder in water and autoclaving to sterilize. Agar plates were filled and allowed to solidify in sterile conditions. Bacterial suspensions were pipetted onto plates using sterile pipettes and glass spreaders. Following intensive screening, none of the bacterial isolates had visible lethal activity against the nematodes or beetle larvae. The results suggest that many factors – environmental and microbial ecology among them – mediate the result. In particular, differences between conditions in laboratory and beetle natural environment (e.g., temperature, humidity, light) can alter bacterial viability and susceptibility of larvae. The work delineates these sources of variability and suggests increasing the replication, environmental conditions control, and testing other inoculation routes (e.g., feeding assays or control direct injection) to improve insecticidal activity assessment.