Susceptibility of house fly (Diptera : Muscidae) larvae to entomopathogenic nematodes (Rhabditida : Heterorhabditidae, Steinernematidae)

The potential for entomopathogenic nematodes to control flies in cattle fee dlots was determined by screening 40 strains representing 8 species of Hete rorhabditis Poinar and 5 species of Steinernema Travassos for virulence tow ard 3rd-instar house flies (maggots), Musca domestica L. None of the 22 str ains of Heterorhabidits infecting maggots caused significant levels of mort ality in a filter paper assay. Ten strains of Steinernema infected maggots. of which 7 strains (4 S. carpocapsae (Weiser), 2 S. feltiae (Filipjev), an d 1 S. scapterisci Nguyen & Smart) caused significant mortality, Ten Hetero rhabditis strains and 10 Steinernema strains successfully reproduced for gr eater than or equal to 2 generations in maggots. No difference was observed between 72-h survival of maggots and adult emergence. Six strains of Stein ernema were selected for 10 generations on maggots and then compared with u nselected Lines. No difference in pathogenicity between selected and unsele cted lines was observed Two strains of S. feltiae, SN and UNK-36, and 2 of the best Heterorhabditis strains, H. bacteriophora Poinar OSWEGO and H. meg idis Poinar, Jackson & Klein HF-85 were tested in a fresh bovine manure sub strate. All 4 strains produced significant fly mortality in the manure subs trate, although the S. feltiae strains had significantly lower LC50 values than did the Heterorhabditis spp. The most promising strain, S. feltiae SN, gave LC50 and LC99 values of 4 and 84 infective juveniles per maggot, resp ectively. These doses were equivalent to 2.7 and 55 infective juveniles per grant of manure and 5.1 and 104 infective juveniles per square centimeter of surface area. Infective juveniles capable of infecting greater wax moth larvae Galleria mellonella (L), survived in manure for up to 10 wk without hosts.