Identifying Biologically-Based Paths Reducing Insecticide Resistance in Codling Moth: Final Report

This final report synthesizes modeling and laboratory work to identify biologically based strategies for managing codling moth resistance, with emphasis on organic systems relying on codling moth granulovirus. The project developed new, generalizable theory for resistance management in biopesticides, distinguishing between (1) parasites whose transmission is linked to host death (e.g., entomopathogenic nematodes) and (2) pathogens that can transmit among living hosts (e.g., viruses). Modeling shows these categories lead to different resistance outcomes and different prospects for “arms race” approaches to improve entomopathogens during rearing.

Empirical trials testing granulovirus plus Steinernema feltiae applied to last instar/pupal stages were ineffective under the study conditions. Life table simulations parameterized for codling moth suggest predator conservation alone has limited effect on slowing insecticide resistance, but predator conservation helps keep pest densities low while reduced insecticide use allows susceptible strains to outcompete resistant strains.