Fipronil:: An ultra-low-dose bait toxicant for control of red imported fire ants (Hymenoptera: Formicidae)

Fipronil, a new broad spectrum pyrazole insecticide, was tested both in the laboratory and field as a bait toxicant for control of red imported fire ants, Solenopsis invicta Buren. Laboratory bioassays with worker ants showed that delayed toxicity occurred with baits ranging from 5 to 200 mu g/ml active ingredient (AI). Tests with field-collected colonies in the laboratory confirmed the bioassay results with worker ants, and demonstrated that granular baits containing from 3.0 to 30 mu g/mg (AI) eliminated colonies in 8 to 11 weeks after treatment. A field trial showed that a 15 mu g/mg granular bait provided over 80% colony mortality at 6 and 12 weeks after broadcast application in non-grazed pastures. These results clearly demonstrate the potential of fipronil for use as a bait toxicant for control of red imported fire ants.