EFFICACY AND PERSISTENCE OF HETERORHABDITIS-MARELATUS (RHABDITIDA, HETERORHABDITIDAE) AGAINST ROOT WEEVILS (COLEOPTERA, CURCULIONIDAE) IN STRAWBERRY

We compared the efficacy of Heterorhabditis marelatus Liu & Berry, a n ewly described species of entomopathogenic nematode, with that of H. b acteriophora Poinar against the root weevils, Ptiorhynchus ovatus (L.) and O. sulcatus in strawberry In the laboratory, H. marelatus was sig nificantly more virulent than H. bacteriophora on O. ovatus and O sulc atus 7 d after nematode application at 14 degrees C. In field experime nts, H. marelatus applied at concentrations of 52 and 136 infective ju veniles (IJs) per square centimeter, reduced root weevil larvae and pu pae 75.3 and 77.4%, respectively, 20 d after nematode application. H. bacteriophora applied at concentrations of 128 and 379 IJs per square centimeter reduced root weevils 50.0 and 74.0%, respectively. Both nem atode species were detected up to 30 d after application by baiting wi th Galleria mellonella larvae in soil samples collected from the field .