Entomopathogenic nematodes for codling moth management in organic apple orchards in Michigan

The codling moth (Cydia Pomonella [L.]) is the most serious insect pest of apples worldwide and is of critical concern in North American apple production. Conventional codling moth management depends on the repeated application of broadly acting contact insecticides targeting either the neonate larva or egg stage of the pest. Final instar codling moth larvae pupate or overwinter in silk cocoons in soil litter and on tree trunks or branches. Entomopathogenic nematodes have potential for management targeting these life stages since they actively search out hosts in cryptic locations. National Organic Program approved formulations of entomopathogenic nematodes are now commercially available for management of a variety of pests, but their effectiveness in the context of organic apple orchard management practices is relatively untested.

The entomopathogenic nematode, Steinernema feltiae (Filipjev) was evaluated for two years at two Michigan organic apple orchards to test its effectiveness for codling moth management in the field under three different application timings. Laboratory bioassays were also used to determine its ability to infect other pests and to determine the impact of commonly used organic fungicides on this nematode’s ability to cause insect mortality. Finally, time series of soil samples from fields where nematodes had been applied were used to determine the persistence of infective juveniles under Michigan orchard conditions. The results of these studies suggest that application timing, soil type, and fungicide applications may influence the effectiveness of entomopathogenic nematodes for pest management in organic apple orchards.