The effect of organic compost and soil texture on the survival and infectivity of entomopathogenic nematode species

To improve the efficacy of entomopathogenic nematodes (EPNs) as biocontrol agents in the field, knowledge about the kinds of impact, which the physical nature of the agricultural soil environment may have on nematode survival, persistence, and host location is important. The study aimed to investigate the effects which the addition of organic soil amendments would have on the duration of infectivity and survivorship of infective juveniles (IJs) belonging to Heterorhabditis bacteriophora in soils undergoing progressive moisture loss. The soil amendments involved mixing commercially available organic compost such as mulch, organic compost, professional potting mix, organic lawn dressing with two soil textural classes, namely loamy soil, and coarse river sand. Using Petri dish-based assays, the mulch soil amendment resulted in the highest Galleria mellonella larval mortality rate across different organic compost application concentrations (mass: mass basis). The type of compost used based on its feedstock composition, the concentration of nutrients, and organic matter mixed with a specific type of soil texture had a significant effect on the tolerance of EPNs to different dehydration periods. Virulence and efficacy decreased over 7 days of progressive dehydration. The use of organic compost did not have any detrimental effect on EPNs. The knowledge obtained could be applied to increase the effectiveness of entomopathogenic nematodes as biocontrol agents.