The effects of soil texture and moisture on the infection of Galleria mellonella L. by entomopathogenic nematodes (Heterorhabditis bacteriophora).

Entomopathogenic nematodes (EPN) show promise for controlling soil dwelling insects. However, edaphic factors may impact the efficacy of EPN on a host. The objectives were to examine the effects of soil texture and moisture on 1) the infection rate of Galleria mellonella by the EPN and; 2) the ability of EPN to move through the soil to find a host at different orientations. Soil textures consisted of sand, a sand/silt/peat mixture, and a silt/peat mixture at 50% and 100% moisture. For the first objective, 45mL of soil and 45,000 Heterorhabditis bacteriophora were placed in petri dishes baited with 10 G. mellonella larvae. For the second objective, one G. mellonella larvae was placed in a 2 cm segment of 1/2 inch PVC pipe filled with soil, oriented in three different directions, and inoculated with 500 H. bacteriophora. A general linear model was used to evaluate infection rates and EPN movement. Both soil moisture (p<0.05) and texture (p<0.05) had significant effects on nematodes infection rates of G. mellonella. Texture, moisture, and orientation did not significantly affect (p>0.05) the ability of EPN to find a host. While EPN were able to find a host within a variety of soil types, soils that held more water had higher infection rates than soils that held less water, suggesting that moisture may be a key component in facilitating infection by EPN. By understanding the factors that influence the ability of EPN to find and infect a host, improved bio-control programs using EPN can be developed.