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°C) and nematode concentrations (0, 100, 500, and 1000). The steinernematid species were unable to cause lethal weevil infections at 10°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°C. LC[sub5][sub0] values for the Tur-H2 and Tur-H1 strains of H. bacteriophora at 15°C, the most probable field application temperature, were 266 and 494 infective juveniles, respectively.
chestnut weevil; curculio elephas; efficacy; heterorhabditis bacteriophora; steinernema carpocapsae; steinernema feltiae