The effect of agitation system, temperature of the spray liquid, nematode concentration, and air injection on the viability ofHeterorhabditis bacteriophora

Entomopathogenic nematodes (EPNs) are a group of potentially effective bio-insecticides to which Heterorhabditis bacteriophora, an active ingredient of several commercialised products, belongs. The application of the spray liquid with a motorised hydraulic sprayer introduces several stress factors to EPNs that may reduce their viability. Therefore, the effects of the agitation system, initial temperature of the spray liquid, EPN concentration, and additional air injection on the viability of EPNs were studied. The results clearly illustrate that the hydraulic agitation caused significantly more reduction in viability than the mechanical agitation. A lower temperature of the initial spray liquid, however, yielded a significantly higher EPN viability compared to a higher temperature after hydraulic mixing and so did air injection while EPN concentration did not significantly influence viability. Thus, the results clearly suggest that, with hydraulic agitation, both the re-circulation stress and the temperature increase significantly decreased the EPN viability, while air injection significantly improved it. Therefore, specific application conditions of living organisms in sprayer design and during application should be considered. Furthermore, spray water of less than 20°C should be used to keep temperature under control.