In vivo production of entomopathogenic nematodes using Galleria mellonella: costs and effect of diets on nematode pathogenicity

Five separate diets – beeswax (BW), glycerol (Gly), and three types of dog croquettes (DC1, DC2, and DC3) – were used to rear larvae of the greater wax moth, Galleria mellonella. The larvae were later inoculated with five different isolates of entomopathogenic nematodes (EPN) emerging from the insect larvae reared on the five diets. Insect cadavers were then conserved for 1, 2, 3, and 4 wks (T1, T2, T3, and T4, respectively) to evaluate the nematodes’ progeny production and to assess the pathogenicity of emerging nematodes to G. mellonella larvae. Larvae fed on DC1 weighed the least (0.18 ± 0.03 g) and those fed on Gly weighed the most (0.22 ± 0.04 g). Gly was effective for insect development but was the most expensive to produce at 6.30 US dollars/kg. No significant difference (P = 0.851) was observed between mortality rates of larvae for nematode isolates for the three best diets (Gly, BW, and DC1) during 1 wk (T1) and 3 wks (T3) after processing at 3 d post-inoculation. All nematode isolates emerged and had the highest population density per insect larva at T1 for isolate Ze4 (Heterorhabditis sonorensis) on BW (553.63 ± 311.97 infective juveniles (IJs)/50 μl of suspension, 276,815 IJs/larva) and at T2 on DC1 (488.63 ± 321.37 IJs/50 μl, 244,315 IJs/larva) and for isolate Aglali (H. sonorensis) at T1 on Gly (615.18 ± 309.63 IJs/50 μl, 307,590 IJs/larva). This study shows the costs and effectiveness of different diets on development and production of G. mellonella larvae and the EPN produced in vivo.