Toxicity and Repellency of Potting Soil Treated with Bifenthrin and Tefluthrin to Red Imported Fire Ants (Hymenoptera: Formicidae)

Abstract

The Lc 50 and LC 90 of bifenthrin in potting soil for female alates of the red imported fire ant, Solenopsis invicta Buren, were 1.1 and 5.2 ppm, respectively. For tefluthrin, the Lc 50 and LC 90 were 8.5 and 19.0 ppm, respectively. These results may provide a basis for setting minimum residue levels for the enforcement of quarantine regulations. Pots filled with soil treated with either bifenthrin or tefluthrin at the label rate of 25 ppm were exposed to small colonies of S. invicta without alternative nesting sites. After 48 h, 6% of the bifenthrin-treated pots and 24% of the tefluthrin-treated pots were considered infested under quarantine standards. When exposure was lengthened to 2 wk, all pots were uninfested. Implications for the imported fire ant quarantine program are discussed.