Recycling Potential and Fitness of Steinernematid Nematodes Cultured in Curculio caryae and Galleria mellonella

Abstract

The recycling potential of entomopathogenic nematodes in the pecan weevil, Curculio caryae, following inundative applications is an important factor in considering whether nematodes could be incorporated into a C. caryae management strategy. Our objective was to determine the recycling potential and fitness of Steinernema carpocapsae and S. riobrave cultured in C. caryae. To estimate fitness and quality, we reared nematodes in larvae of C. caryae and in the commonly used standard host, the greater wax moth, Galleria mellonella. Nematode lipid content, infectivity (power to invade), virulence (power to kill), and reproductive capacity (yield per insect) in C. caryae larvae were compared with G. mellonella data. Lipid content was higher in S. carpocapsae cultured in C. caryae than in G. mellonella, but S. riobrave lipid content was not affected by host source. Host source did not affect subsequent infectivity or virulence to C. caryae (P 0.05) but did affect reproductive capacity (P 0.0001). Both nematode species produced more progeny in C. caryae when they were first cultured in G. mellonella than when they were first passed through C. caryae. In terms of potential to recycle under field conditions, we predict that nematodes resulting from one round of recycling in C. caryae larvae would be equally capable of infecting and killing more weevils, but the potential to continue recycling in C. caryae would diminish over time due to reduced reproduction in that host.