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

Authors: Oi, David; Atchison, Rachel; OLIVER, JASON - Tennessee State University; WEEKS, RONALD - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2026
Publication Date: 3/7/2026
Citation: Oi, D.H., Atchison, R.A., Oliver, J.B., Weeks, R.D. 2026. Non-repellent insecticide disinfests red imported fire ants (Hymenoptera: Formicidae) from field-harvested nursery plants. Journal of Economic Entomology. 00:1-9. https://doi.org/10.1093/jee/toag037.
DOI: https://doi.org/10.1093/jee/toag037

Interpretive Summary: The spread of fire ants in the US has been linked to infested nursery plants which has resulted in a quarantine that requires plants to be fire ant-free before their shipment beyond quarantined areas. Large, field-grown nursery plants, such as trees, are shipped with their root balls (roots and soil wrapped in burlap), which are a prime harborage for fire ants. In a collaborative project, among APHIS (Raleigh, NC), Tennessee State University (McMinnville, TN), and ARS, CMAVE (Gainesville, FL), to improve quarantine protocols for the elimination of fire ants from root balls, the effectiveness of non-repellent insecticides was evaluated. Observations of excavated soil on the surface of fire ant infested root balls indicated that fire ants are normally active at the burlap and soil interface. Applying insecticides to the surface of root balls that are not repellent, yet toxic, to fire ants should be effective because they would not deter fire ant contact with treated burlap and soil. Comparisons of spray applications of several non-repellent insecticides to the surface of fire ant infested root balls resulted in 75% of the root balls becoming completely disinfested of fire ants. In contrast, 75 – 100% of the root balls sprayed with the repellent insecticide bifenthrin or a combination of bifenthrin and other non-repellents remained infested. In addition, dinotefuran prevented migrating fire ant colonies from infesting root balls for 6 months, while bifenthrin drench applications prevented infestations in 66% of the root balls. Based on the results of these studies, the surface spray application of the non-repellent dinotefuran to root balls should be evaluated further on large root balls as a potential new quarantine treatment for field-grown nursery plants.

Technical Abstract: The spread of red imported fire ants (RIFA), 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 (FIFAQ). 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 RIFA from root balls was evaluated. Surface spray applications of non-repellent insecticides with the active ingredients of dinotefuran or indoxacarb disinfested 75% of root balls harboring RIFA. Excavated soil observed on the surface of root balls before treatments suggested that RIFA are normally active at the burlap and soil interface. Non-repellent insecticides sprayed on the root ball may be effective because they would not deter RIFA contact with treated substrate. 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 RIFA infestations for 6 months 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 FIFAQ treatment for field-grown nursery plants.