We studied the interactions between F1 progeny of Pectinophora gossypiella (Saunders) adults irradiated in the pupal stage and entomopathogenic nematodes. Both sexes of pink bollworm pupae were exposed to 4, 8, 12, or 16 krad substerilizing radiation doses irradiated using a 60Co source. The F1 larvae were tested in a sand bioassay for susceptibility to Steinernema riobravis Cabanillas, Poinar & Raulston, S. carpocapsae (Weiser), and 2 strains of Heterorhabditis bacteriophora (Poinar). The numbers of infecting nematodes were counted after 48 h. Increasing parental radiation dose significantly increased F1 larval susceptibility to S. riobravis and H. bacteriophora, but decreased susceptibility to S. carpocapsae. This difference in susceptibility may be caused by the sedentary nature of larvae from parents receiving higher levels of irradiation, combined with the passive ambush tactics used by S. carpocapsae to acquire an insect host. The need to sustain the F1 population of pink bollworm for sterility promotion and subsequent population collapse suggests S. carpocapsae to be an ideal entomopathogenic nematode to be used in conjunction with inherited sterility control methods.
In laboratory bioassays Steinemema riobrave Cabanillas, Poinar and Raulston (355 strain), S. carpocapsae (Weiser) (Mexican 33 strain), S.feltiae (Filipjev) (UK76 strain), and Heterorhabditis bacteriophora Poinar (HP88 strain) infected and killed the subterranean termite, Heterotermes aureus (Snyder). Steinemema carpocapsae, S. riobrave and H. bacteriophora successfully reproduced in H. aureus and infective juveniles (IJs) exited the termite cadavers successfully. However, no progeny were produced by S.feltiae. IJs of S. carpocapsae formed two distinct size groups. The average total body length for the smaller group was 299.5 μm (S.E. 4.8), the average total body length for the larger group was 545.6 μm (S.E. 6.0). Small S. carpocapsae IJs infect, reproduce and form normal size IJs after subsequent infection in Galleria mellonella L. S. riobrave and H. bacteriophora showed a more gradual recovery in IJ size that needed 2 infection cycles in G. mellonella. In termite mortality tests, the progeny of small IJs of S. carpocapsae are comparably effective to the normal size IJs, under the conditions tested. After 72-h S. riobrave IJs from stock cultures (reared in G. mellonella) caused higher termite mortality compared with IJs cycled through termites then G. mellonella, then applied to termites. © The Society of Nematologists 2008.