Biocontrol of black cricket, Gryllus bimaculatus (Orthoptera: Gryllidae) nymphs with entomopathogenic nematodes

Abstract

Entomopathogenic nematodes Steinernema carpocapsae, S. feltiae (Steinernematids) Heterorhabditis indica and H. bacteriophora (Heterorhabditids) were studied to control nymphs of black cricket Gryllus bimaculatus. Larvae (6th instar) of Galleria mellonella were infected in order to obtain culture of four different infective juveniles (IJs) of entomopathogenic nematodes S. carpocapsae (All isolate, cultured at 25 °C), S. feltiae (cultured at 25 °C), H. bacteriophora (HW79 isolate, cultured at 28 °C) and H. indica (Pakistani isolate, cultured at 28 °C). S. carpocapsae and S. feltiae were stored at 7 °C while other two viz., H. indica and H. bacteriophora were stored at 15°C. Results of all the experiments showed a significant difference in mortality percentage among all isolates. All the nematodes were found more effective when exposure time increased up to 8 days. S. carpocapsae showed better mortality, more prod uction of infective juveniles (IJs) and maximum infectivity of black cricket nymphs as compared to other nematodes at 25 °C. On the other hand, both Heterorhabditids caused maximum mortality, production and infectivity as compared to two Steinernematids at 30 ° C. When different dose concentration levels were tested in the sand arena, all dose concentrations resulted satisfactory mortality but a high level of dose concentration (400 IJs / ml) caused maximum insect mortality in all isolates. A similar response was observed in infectivity test when maximum percentage of IJs of both isolates of Heterorhabditis successfully penetrated into nymphs of G. bimaculatus. This research suggests some useful basic findings with suitable virulent selection of entomopathogenic nematodes for controlling nymphs of G. bimaculatus.