Effcacy of the entomopathogenic nematode Heterorhabditis bacteriophora using diferent application methods in the presence or absence of a natural enemy

Abstract

Various application methods for the entomopathogenic nematode Heterorhabditis bacteriophora were evaluated underlaboratory and feld conditions. Four diferent methods of applying the infective juveniles (IJs) of the nematode to soil were assessedincluding (1) insect cadavers (referred to as nematode-infected cadavers), (2) subsurface injection, (3) spraying, and (4) drip irrigation.In the laboratory experiment, except for the control with no nematodes, all treatments showed more than 95% insect mortality ofthe bait insect (Galleria mellonella ) with no signifcant diferences among treatments. Te same experimental setup was conductedwith the introduction of mites, Sancassania polyphyllae (Acari: Acaridae), which are natural enemies of entomopathogenic nematodes.Te treatment groups with mites and the control group without mites showed more than 87% insect mortality and no signifcantdiferences were observed. Te nematode-infected cadaver application method was further evaluated by using cadavers of diferent agescontaining H. bacteriophora IJs in the presence of mites. Larval mortality of the bait insect was signifcantly lower when 3- or 6-day- old nematode-insect cadavers were used in the presence of mites. Diferent application methods were also tested in a corn feld. Nosignifcant diferences were observed among the application methods. Our results indicate that the diferent application methods had nosignifcant effect on larval mortality, but the presence of mites had a negative effect on the cadaver application when the cadavers were3 days old but had no signifcant efect when the cadavers were 6 and 9 days old.