Virulence of three species of entomopathogenic nematodes to the chestnut weevil, Curculio elephas (Coleoptera: Curculionidae)

Indigenous entomopathogenic nematodes were evaluated in laboratory soil cup experiments as candidates for management of the chestnut weevil, Curculio elephas (Coleoptera: Curculionidae), the most severe insect pest of chestnut in Turkey. Three entomopathogenic nematode species, Steinernema carpocapsae (Anamur strain), S. feltiae (Tur-S3 strain), and Heterorhabditis bacteriophora (Tur-H1 and Tur-H2 strains) (Rhabditida: Steinernematidae, Heterorhabditidae) were bioassayed against last-instar weevils at different temperatures (10, 15, and 25 degrees C) and nematode concentrations (0, 100, 500, and 1000). The steinernematid species were unable to cause lethal weevil infections at 10 degrees C whereas the heterorhabditid strains still induced 21-22% host mortality. The Tur-H2 strain of H. bacteriophora was the most virulent nematode at all temperatures tested, most notably killing 96.5% of weevil larvae at 25 degrees C. LC50 values for the Tur-H2 and Tur-H1 strains of H. bacteriophora at 15 degrees C, the most probable field application temperature, were 266 and 494 infective juveniles, respectively.