Evaluating complementarity between codling moth entomopathogens

Codling moth is the key pest of US apples and pears. Granulovirus is often used to control codling moth in organic production, but resistance to granulovirus in codling moth has been identified in Europe and may also occur in the United States. Entomopathogenic nematodes are also used for codling moth control, and can also be used in organic production, but their effectiveness was shown on larvae pupating in the soil and not on tree trunks or leaf litter where they are often found. While nematodes attack codling moth as pupae, the granulovirus infects them as larvae, so we hypothesized that prior sublethal exposure from granulovirus would weaken the moths’ immune systems and cause them to be more susceptible to the nematodes. We tested this hypothesis in a mesocosm experiment. We found mature larval contact with granulovirus insufficient for detectable synergistic effects, and direct spray with nematode solution while pupating on a surface to be ineffective in causing infection.