BIOLOGICAL CONTROLÑMICROBIALS Survey of Entomopathogenic Nematodes and Fungi Endemic to Pecan Orchards of the Southeastern United States and Their Virulence to the Pecan Weevil (Coleoptera: Curculionidae)

Thepecanweevil,Curculio caryae (Horn), is amajor pest of pecans in the Southeastern United States. Entomopathogenic nematodes and fungi are potential alternatives to chemical insecticides for C. caryae control. Our objective was to survey pecan orchards in the southeastern United States for entomopathogenic nematodes and fungi and determine the virulence of the new isolates to C. caryae larvae. Soil was collected from 105 sites in 21 orchards in Arkansas, Georgia, Louisiana, and Mississippi. Entomopathogens were isolated by exposing soil to C. caryae and greater wax moth larvae, Galleria mellonella, (L.). We isolated entomopathogenic fungi and nematodes from 16 and 6 of the 21 orchards surveyed, respectively. The entomopathogenic fungi included Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin, and nematodes included Heterorhabditis bacteriophora Poinar, Steinernema carpocapsae (Weiser), Steinernema glaseri (Steiner), and Steinernema rarum (Doucet). This is the Þrst report of Steinernema rarum in theUnited States. Soil characteristics in orchards were analyzed for pH, organic matter, and nutrients; we detectedanegative relationshipbetween fungal occurrenceandmanganese levels in soil andapositive relationship betweenM. anisopliae occurrence and calcium ormagnesium levels. In laboratory assays, virulence of 15 nematode and 22 fungal isolates to C. caryae larvae was tested in small plastic cups containing soil. Results indicated poor susceptibility of the C. caryae larvae to entomopathogenic nematodes. Several fungal isolates that caused signiÞcantly higher mortality in C. caryae larvae than other strains (including a commercial strain ofB. bassiana) should be investigated further as potential control agents of C. caryae.