Virulence of entomopathogenic nematodes to Diaprepes abbreviatus (Coleoptera: Curculionidae) in the laboratory

The Diaprepes root weevil, Diaprepes abbreviatus (L.) is the most severe weevil pest in Florida citrus. Entomopathogenic nematodes have effectively suppressed larval populations of D. abbreviatus. Our objective was to conduct a broad laboratory comparison of entomopathogenic nematodes for virulence toward larvae of D. abbreviatus. The study was conducted at three temperatures (20, 24, and 29 degrees C) and included nine entomopathogenic species and 17 strains: Heterorhabditis bacteriophora Poinar (Baine, NJl, Hb, Hbl, HP88, and Lewiston strains), H. indica Poinar, Karunakar & David (original and Homl strains), H. marelatus Liu & Berry (IN and Point Reyes strains), H. megidis Poinar, Jackson & Klein (UK21l strain), H. zealandica Poinar (NZH3 strain), Steinernema riobrave Cabanillas, Poinar & Raulston (355 strain), S. carpocapsae (Weiser) (All strain), S. feltiae (Filipjev) (SN and UK76 strains), and S. glaseri (Steiner) (NJ43 strain). At 20 degrees C, the greatest mortality was caused by S. riobrave although it was not significantly greater than H. bacteriophora (Baine), H. bacteriophora (Hb), H. bacteriophora (Hbl), and H. indica (original). At 24 and 29 degrees C, S. riobrave caused greater larval mortality than other nematodes tested. Two strains of H. indica, H. bacteriophora (Baine), and S. glaseri were next in terms of virulence at 29 degrees C. Our results suggest that S. riobrave has the greatest potential for control of D. abbreviatus.