RAPID COMMUNICATION Susceptibility of the Strawberry Crown Moth (Lepidoptera: Sesiidae) to Entomopathogenic Nematodes

The objective of this studywas to determine the susceptibility of the strawberry crown moth, Synanthedon bibionipennis (Boisduval) (Lepidoptera: Sesiidae) larvae to two species of entomopathogenic nematodes. The entomopathogenic nematodes Steinernema carpocapsae (Weiser) strain Agriotos and Heterorhabditis bacteriophora (Steiner) strain Oswego were evaluated in laboratory soil bioassays and the Þeld. Both nematode species were highly infective in the laboratory bioassays. Last instars were extremely susceptible to nematode infection in the laboratory, even in the protected environment inside the strawberry (Fragaria ananassa Duch.) crown. Infectivity in the laboratory was 96 and 94% for S. carpocapsae and H. bacteriophora, respectively. Field applications in late fall (October)were less effectivewith S. carpocapsae andH. bacteriophora, resulting in 51 and 33% infection, respectively. Larval mortality in the Þeld from both nematode treatments was signiÞcantly greater than the control, but treatments were substantially less efÞcacious than in the laboratory. Soil temperature after nematode applications in the Þeld (11 C mean daily temperature) was below minimumestablishment temperatures for bothnematode species for amajority of thepost-application period. It is clear from laboratory data that strawberry crown moth larvae are extremely susceptible to nematode infection. Improved control in the Þeld is likely if nematode applications aremade in late summer to early fall when larvae are present in the soil and soil temperatures are more favorable for nematode infection.