Using entomopathogenic nematodes to manage codling moth in Michigan apple orchards

Entomopathogenic nematodes are tiny parasites of insects that can be applied in a water mixture and can kill their hosts within only a few hours after infection.  The codling moth (Cydia Pomonella [L.]) is a serious pest of apples worldwide and is of critical concern in organic apple production. Codling moth larvae pupate and overwinter in silk cocoons in soil surface litter and under the bark on tree trunks. Entomopathogenic nematodes have potential for management targeting codling moth larvae since they actively search out hosts in these types of protected locations. We have been evaluating the entomopathogenic nematodes species, Steinernema feltiae (Filipjev), at three Michigan organic apple orchards to test its effectiveness for codling moth management. Our previous research had indicated that nematode applications were more effective in orchards planted with smooth-barked tree varieties, presumably because the codling moth larvae in these orchards were forced to overwinter on the orchard floor where they were more susceptible to infection by entomopathogenic nematodes. This poster presents the results of our experiment testing the hypothesis that codling moth larvae in cocoons on the orchard floor are more susceptible to nematode sprays than those in other locations in the orchard. We found that S. feltiae applied with a backpack sprayer were able to successfully infect sentinel codling moth larvae in sheltered and unsheltered locations on the trunk and in unsheltered locations on the orchard floor. However, larvae that were under wooden shelters on the soil surface did not exhibit increased infection in nematode treated plots compared to those in untreated plots. This result implies that S. feltiae may not be as effective at reaching codling moth larvae in protected locations on the orchard floor as previously thought.