Non-repellent insecticide disinfests red imported fire ants (Hymenoptera: Formicidae) from field-harvested nursery...

The spread of red imported fire ants, Solenopsis invicta Buren, has been linked to the shipment of infested nursery plants, and their movement is regulated under the Federal Imported Fire Ant Quarantine. Fire ants are difficult to disinfest from large, field-grown plants with roots and soil wrapped in burlap (root balls). The efficacy of non-repellent insecticides to eliminate red imported fire ants from root balls was evaluated. We hypothesized that non-repellent insecticides sprayed on root balls would be effective because they would not deter red imported fire ants contact with treated substrate. Surface spray applications of non-repellent insecticides with the active ingredients of dinotefuran or indoxacarb disinfested 75% of root balls harboring red imported fire ants. Dinotefuran was tested at lower concentrations to potentially reduce treatment costs. While reductions in adult counts and brood volume were >90%, which differed significantly from the control, no differences were detected in the numbers of infested root balls among dinotefuran concentrations. The residual efficacy of dinotefuran at the full label rate prevented red imported fire ant infestations for 6 mo, while the half-rate of dinotefuran, a bifenthrin drench, and the control all had infested root balls. Based on the results of these studies, the surface spray application of the non-repellent dinotefuran to root balls should be examined further as a potential Federal Imported Fire Ant Quarantine treatment for field-grown nursery plants.