Acceptance of fire ant baits by nontarget ants in Florida and California

Abstract Red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), infestations can be cleared from areas with baits, but these areas are often reinfested. To facilitate biotic resistance strategies to reinfestation, acceptance of eight commercial fire ant baits by nontarget ants was examined in Florida and California. Baits contained active ingredients of either indoxacarb, spinosad, abamectin, pyriproxyfen, metaflumizone, hydramethylnon, and/or (s)-methoprene. In Florida, baits were tested on Monomorium floricola (Jerdon), Dorymyrmex bureni (Trager); Pheidole megacephala (Fabricius), and Pogonomyrmex badius (Latreille). The percentages of the total number of ants that accepted baits were not statistically different among the eight fire ant baits by species. Among the baits and nontarget species evaluated in Florida, baits with solely (s)-methoprene or metaflumizone as the active ingredient had the lowest average percentages of bait acceptance (0.7 and 1.6, respectively). In California, tests were conducted with Pogonomyrmex californicus Buckley, large and small-sized Dorymyrmex bicolor Wheeler, Forelius pruinosus Roger, a species from the Pheidole crassicornis group, and a Myrmecocystus sp. Significant differences in bait acceptance for each species were not detected among five baits containing indoxacarb, pyriproxyfen, metaflumizone, (s)-methoprene, and/or hydramethylnon. Based on mean percentages of bait acceptance and observations of bait feeding, there was inconsistent bait acceptance by F. pruinosus and P. crassicornis group. Myrmecocystus sp. did not accept any fire ant bait. None of the fire ant bait products tested exhibited non-acceptance by all the nontarget ant species assayed. To conserve nontarget ants, fire ant bait selection will need to consider the nontarget ants present at individual sites and specific bait(s), that are least accepted by these ants.