Biological characteristics of high-searching individuals of the Heterorhabditis bacteriophora HBH hybrid strain for use in biocontrol

Abstract

Entomopathogenic nematodes (EPNs) are widely used in biological control to manage insect pests. The present study aimed to select individuals with enhanced host-seeking abilities from the Heterorhabditis bacteriophora HBH hybrid strain using an apparatus and the selected individuals were then compared with the original strain in terms of infectivity, reproductive capacity, and storage survival. Initially, last-stage Galleria mellonella larvae were placed in a plastic cage at the bottom of the apparatus. Subsequently, 1000 infective juveniles (IJs) were transferred to the upper part of the apparatus, and kept at 25 degrees C. This process was repeated until the fifth generation was obtained. The fifth-generation individuals (termed HBH Plus) were then compared with those of the HBH hybrid strain. The results indicated that the highest efficacy of the selected individuals (HBH Plus) against G. mellonella and Tenebrio molitor larvae, Rhizopertha dominica, and Oryzaephilus surinamensis adults was 90, 73.33, 86.67, and 83.33 %, respectively. For the parental culture, these values were 76.67, 63.33, 73.33 and 73.33 %, respectively. When reproductive capacity was examined, HBH Plus producing an average of 125.333,33 IJs per G. mellonella larva, versus 108.741,67 in the parental strain per G. mellonella larva. An increase in mortality rates in the IJ stages was observed with the extension of the storage duration in both the HBH hybrid strain and HBH Plus individuals. HBH Plus reached a mortality rate of 20.21 % by month five. These findings suggest that selection for enhanced host-seeking behavior in EPNs can improve their biological control potential.