Abstract
Top‐down population regulation can influence the success of biological control agents when they are released into the field. Entomopathogenic nematodes (EPNs) are used commonly in biological control programmes, but their efficacy suffers from poor persistence. Although abiotic soil conditions have been shown to reduceEPNpersistence, consumption of infected insects by scavengers and of infective juvenile (IJ) nematodes by predators may also regulate these populations. In the present study, the effects of different soil arthropods onEPNs in laboratory conditions were measured. It was hypothesised that arthropods commonly found in soil communities whereEPNs are applied would consume cadavers of insects parasitised by the nematodes and theIJs themselves.Some species of scavengers consumeEPN‐infected insects. Crickets (Gryllus bimaculatusDe Geer),American cockroaches [Periplaneta Americana(Linnaeus)], ants [Tetramorium chefketiForel andPheidole pallidula(Nylander)], earwigs (Labidura ripariaPallas), mites (Sancassania polyphyllaeZachvatkin), and springtails (Sinella curvisetaBrook andFolsomia candidaWillem) have different responses to nematode‐killed insects. Results suggested that ants (T. chefketi), cockroaches, mites, and earwigs fed onSteinernema‐killed insects whereas neither crickets nor springtails consumed them.In the second part of the study, experiments were conducted to determine whether mites and springtails consumedIJ EPNs. Results showed thatS. polyphyllaemites do not consume infective juveniles in soil, whereas both springtail species consumed significant numbers of theIJs.Top‐down regulatory processes can be a limiting factor forEPNpopulations under laboratory conditions. Both host cadavers andIJs are consumed (albeit by different arthropods), so these results may help explain the difficulties associated with the persistence ofEPNapplication to soil.
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