Effects of combining an entomopathogenic fungi or bacterium with entomopathogenic nematodes on mortality of Curculio caryae (Coleoptera: Curculionidae)

Our objective was to determine the effects of combining entomopathogenic nematodes with other entomopathogens on their ability to suppress larvae of the pecan weevil, Curculio caryae. In laboratory assays, we simultaneously applied the nematodes Heterorhabditis indica or Steinernema carpocapsae with the fungus Beauveria bassiana, Metarhizium anisopliae, or Paecilomyces fumosoroseus, or the bacterium Serratia marcescens. Mortality of C. caryae was determined 14 days after application. We observed antagonism in all pathogen combinations, except H. indica combined with M. anisopliae, for which additive effects were observed. The combination of H. indica and M. anisopliae may merit further study in other systems. Depending on application rate, S. carpocapsae combined with B. bassiana or S. marcescens also resulted in additivity. S. carpocapsae (applied alone) generally caused greater C. caryae mortality than other pathogens applied alone. P. fumosoroseus and S. marcescens were not pathogenic to C. caryae when applied alone. We conclude that the pathogen combinations we investigated are not likely to improve suppression of C. caryae larvae beyond what is expected from single application of the pathogen with greatest virulence.