Potential Role of Nematophagous Microarthropods as Biotic Mortality Factors of Entomogenous Nematodes (Rhabditida: Steinernematidae, Heterorhabditidae)

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Abstract
Potential for nematophagous mites and Collembola to reduce survival of entomogenous nematodes was tested in laboratory studies. The majority of the arthropods tested were observed feeding on Steinernema feltiae Filipjev (Breton strain) and Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann) (NC strain) infective stage juveniles. Phoresy of S. feltiae infectives on many of the mites was observed, with infectives forming rafts of tightly packed nematodes on the dorsum of some of the larger mites. Such infectives remained viable and could move off the mite to kill prepupae of the greater wax moth, Galleria mellonella (L.). Only one species of mesostigmatid mite, Gamasellodes vermivorax Walter, was able to complete development on infectives, and survival was poor. An endeostigmatid mite, Alycus roseus Koch, and a collembolan, Hypogastura scotti Yosii, were able to complete development from late-instar nymph to adult and to produce viable eggs on S. feltiae. In laboratory studies, there was a negative correlation between G. vermivorax number and greater wax moth prepupal mortality, demonstrating lossin nematode efficacy caused by predation by the mesostigmatid mite. There was also a significant difference between LD50 estimates obtained when mites were present or absent. Thus, nematophagous micro arthropods are a biotic factor that could limit survival of field-applied entomogenous nematodes.