Optimization of inoculation techniques for in vivo mass culture of entomopathogenic nematodes through nematode and insect host manipulation

摘要

Three different inoculation treatments were compared, using Galleria mellonella Linnaeus (Lepidoptera: Pyralidae) and Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae) as hosts, and Heterorhabditis bacteriophora Poinar and H. zealandica Poinar asinoculum. The highest percentage infection of insect hosts was achieved by pipetting nematodes onto hosts, followed by immersion of hosts into nematode suspensions, and, lastly, by shaking hosts together with nematode inoculum. Mealworm larvae were exposed to 70 °C tap water in an attempt to compromise their defence mechanisms prior to inoculation. Infection levels of 12 % for H. bacteriophora and 21 % for H. zealandica obtained were lower than that of the control. Pre-inoculation treatment of infective juveniles with Mn~(2+)S0_4.H_20 also did not significantly increase infection rates. Mealworm infection was 81 % for treated H. zealandica in comparison to 80 % for the control. Using treated H. bacteriophora, infection levels of mealworms were 47 %, compared to the control at 48 %. Host and nematode stress or methods tested did not lead to an improvement in infection levels, contrary to previous findings in literature.