ENTOMOPATHOGENIC NEMATODE INFECTIVITY ASSAY - COMPARISON OF PENETRATION RATE INTO DIFFERENT HOSTS

Penetration rate (the percentage of the initial infective juvenile ino culum that invades an insect host) was rested as an indicator of entom opathogenic nematode infectivity. Several host-parasite-substrate comb inations were evaluated for penetration rate. Four steinernematids, St einernema carpocapsae, S. glaseri, S. feltiae, S. riobravis and two st rains of Heterorhabditis bacteriophora were tested in a contact bioass ay against the wax moth, Galleria mellonella, the yellow meal worm, Te nebrio molitor, tile beef armyworm, Spodoptera exigua, the black cutwo rm, Agrotis ipsilon, and the European com borer, Ostrinia nubilalis. T he insect larvae were confined individually in sand and filter paper a renas and exposed to 200 infective juveniles. After incubation, dean i nsects were dissected in order to count the nematodes penetrated. The data were analyzed for the effects of nematode strain and substrate on penetration rate. The bioassay substrate had a variable effect depend ing or? the insect species. The nematode effect was highly significant for all insects tested. The penetration rate therefore allowed compar isons among nematode strains invading a host. Nematode ranking for inf ectivity differed according to the insect tested.