ARS | Publication request: TO WHAT EXTENT CAN BENEFICIAL INSECT-KILLING NEMATODES REPRODUCE IN PECAN WEEVILS?

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: May 17, 2005
Publication Date: June 1, 2005
Citation: Shapiro Ilan, D.I., Dutcher, J.D. 2005. To what extent can beneficial insect-killing nematodes reproduce in pecan weevils?. Pecan Grower. 17(1):15-18.

Interpretive Summary: The pecan weevil is a key pest of pecans. We are seeking new environmentally sound methods of controlling this pest. Insect-killing nematodes are small round worms that kill insect pests but don't harm people or the environment. Initial studies indicate that these nematodes are promising alternatives for pecan weevil suppression. The effectiveness of using nematodes to control the pecan weevil will depend, in part, on how well the nematodes can reproduce inside the dead insect, and how well emerging (progeny) nematodes can go on to kill new weevils. In this study, we found that nematodes can reproduce in pecan weevil larvae, and the nematode progeny that emerge from dead pecan weevils are fully capable of killing more pecan weevils. However, the ability of the nematode progeny to continually reproduce in pecan weevil through multiple generations or seasons appears to diminish over time, thus re-application of nematodes will likely be necessary.

Technical Abstract: The recycling potential of entomopathogenic nematodes in the pecan weevil, Curculio caryae, 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 of S. carpocapsae and S. riobrave cultured in C. caryae larvae. Host source did not affect subsequent virulence to C. caryae, but did affect reproductive capacity. 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.