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 i n the laboratory and field as a bait toxicant for control of red impor ted fire ants, Solenopsis invicta Buren. Laboratory bioassays with wor ker ants showed that delayed toxicity occurred with baits ranging from 5 to 200 mu g/ml active ingredient (AI). Tests with field-collected c olonies in the laboratory confirmed the bioassay results with worker a nts, 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 fie ld trial showed that a 15 mu g/mg granular bait provided over 80% colo ny mortality at 6 and 12 weeks after broadcast application in non-graz ed pastures. These results clearly demonstrate the potential of fipron il for use as a bait toxicant for control of red imported fire ants.