A comparison of insecticide susceptibility levels in 12 species of urban pest ants with special focus on the odorous house ant, Tapinoma sessile.

BACKGROUND: Many ant species are pests in urban, agricultural, and natural habitats around the world. The primary means of reducing or eliminating ant infestations utilizes chemical control, mainly applications of residual insecticides. Control failures with residual insecticides are common, driven in part by a lack of understanding of basic biological and life history characteristics, including interspecific variation in susceptibility to insecticides. The current study evaluated the susceptibility of 12 species of urban pest ants to three classes of insecticides.

RESULTS: Results show significant variation in susceptibility across species. Contrary to the hypothesis of proportionality, no significant relationship was detected between body mass and median lethal time (LT50 ) or time to 100% mortality. The odorous house ant (Tapinoma sessile) was consistently the least susceptible to all insecticides, as indicated by the highest LT50 values and the greatest amount of time required to reach 100% mortality. Comparatively low susceptibility to commonly used spray insecticides may explain why T. sessile is such a persistent pest. Broadcast applications of spray insecticides may kill off the most susceptible species, leaving behind T. sessile. Lack of competition from other ant species, combined with increased access to nesting and feeding resources may allow T. sessile to fill a vacant ecological niche and expand its range.

CONCLUSION: Considering T. sessile's relatively low susceptibility to insecticides, its ability to become established in areas colonized by other invasive ants, and its highly invasive behaviors, it should be watched for by biosecurity programs as it has high potential to become a globally invasive pest. © 2021 Society of Chemical Industry.