Field evaluation of aerial applications of hydramethylnon and metaflumizone to control the red imported fire ant, Solenopsis invicta (Buren) and related ant species (Hymenoptera: formicidae)

The red imported fire ant (RIFA) was introduced to the United States from South America over 75 years ago, and has become a pest in wildlife settings. Hydramethylnon fire ant bait has been the industry standard for controlling the red imported fire ant. It can be compared to novel baits, and used to evaluate different aerial application techniques, such as the "skip swath" method. Two baits, hydramethylnon and metaflumizone, and a skipped-swath method were evaluated through observations of the activity levels of RIFA mounds and abundance. The effects of RIFA on other ant species were determined by eliminating RIFA with insecticides, and then sampling for all remaining ant species. Measurements of RIFA mound activity was done by recording their response to the vibration of wire flags located in active mounds. This method indicated control of RIFA with hydramethylnon and metaflumizone from 61 to 180 d post-treatment. Additional monitoring for RIFA activity, in the same plots, was done with baited vials. These results indicated that complete control of RIFA was never achieved with either hydramethylnon or metaflumizone within 180 d post-treatment; however, there were significant reductions in RIFA population as a result of both chemical baits from 3-92 d post-treatment. A reduction of RIFA populations occurred with both baits, as determined through scheduled sampling of all ant species using baited vials. Native ants, such as Dorymyrmex spp., were found in higher numbers once RIFA populations were reduced, indicating that the two ant species compete for resources such as food and space. Dorymyrmex spp. numbers were suppressed by RIFA populations, while other ants, such as Paratrechina spp. were unaffected.