REGIONAL VARIATION IN INSECTICIDE SUSCEPTIBILITY IN ODOROUS HOUSE ANTS (TAPINOMA SESSILE)

The odorous house ant (Tapinoma sessile) is an adaptive and widespread pest ant species found in North America. Despite the economic and ecological impact of pest ants, effective management still faces many challenges and control failures with liquid spray insecticides in urban and natural environments. In many insects such as bed bugs and cockroaches, chemical control measures have resulted in insecticide resistance. However, in contrast to non-social insects, insecticide resistance has never been documented in social insects. The current study had three main goals. The first objective was to examine regional variation in T. sessile insecticide susceptibility to three classes of insecticides commonly used in urban ant control. The second objective was to compare insecticide susceptibility in T. sessile colonies collected in natural vs. urban areas. The final objective was to determine if insecticide susceptibility varies in workers vs. queens. A total of 30 T. sessile colonies were collected within a 50-mile radius of Purdue University campus, Tippecanoe County, Indiana. Fifteen colonies were collected in natural areas and 15 in urban areas. Insecticide susceptibility of all 30 colonies was tested using residual exposure assays. Urban and natural colonies showed no significant differences in tests with lambda-cyhalothrin and fipronil. In tests with dinotefuran, urban colonies were significantly more tolerant relative to natural colonies. These results suggest that habitat type does not reliably predict susceptibility levels in individual populations. Queens were found to be significantly more tolerant relative to their worker counterparts across all three insecticides. Lower insecticide susceptibility in the queens may explain why T. sessile is such a persistent pest in urban environments. This 15 study’s results can in part provide a foundation for the development of more effective and efficient control methods for T. sessile.