Post-harvest pyrethroid drench and injection treatments for quarantine control of imported fire ant (Hymenoptera: Formicidae) colonies infesting field-grown nursery plants

Authors: OLIVER, JASON - Tennessee State University; ADDESSO, KARLA - Tennessee State University; Oi, David; YOUSSEF, NADEER - Tennessee State University; O’NEAL, PAUL - Tennessee State University; Atchison, Rachel; ALEXANDER, LISA - US Department Of Agriculture (USDA); WEEKS, RONALD - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2025
Publication Date: 2/11/2026
Citation: Oliver, J.B., Addesso, K.M., Oi, D.H., Youssef, N.N., O’Neal, P., Atchison, R.A., Alexander, L.W., Weeks, R.D. 2026. Post-harvest pyrethroid drench and injection treatments for quarantine control of imported fire ant (Hymenoptera: Formicidae) colonies infesting field-grown nursery plants. Journal of Economic Entomology. 119(2):974-981. https://doi.org/10.1093/jee/toag004.
DOI: https://doi.org/10.1093/jee/toag004

Interpretive Summary: There is a fire ant quarantine in the US to prevent human assisted spread of these invasive, stinging ants. Quarantine regulated articles, must be treated following approved protocols and must not be infested with fire ant queens or reproducing colonies. Of particular risk are large, field-grown nursery plants, such as trees, with soil-containing root balls that are typically wrapped in burlap and shipped beyond the quarantined areas. Large plants are difficult to treat effectively with approved treatments of 1) immersing in insecticide solutions of chlorpyrifos or bifenthrin; or 2) thoroughly drenching root balls with chlorpyrifos. The immersion method is impractical for nursery growers and chlorpyrifos may become unavailble. To improve quarantine treatments, scientists at ARS, CMAVE in Gainesville, FL, Tennesse State University and ARS in McMinnville, TN, and in collaboration with APHIS, Raleigh, NC, determined the effectiveness of drench plus injection applications of the insecticides a) bifenthrin and b) lambda-cyhalothrin, c) the standard drench of chlorpyrifos, and d) a drench of water, to disinfest fire ant colonies from trees with large root balls. Bifenthrin and lambda-cyhalothrin eliminated all fire ant colonies in 2 weeks, while > 70% of the chlorpyrifos and the water drenched root balls were infested. To assess the effectiveness of the above treatments in preventing new fire ant queens from starting colonies in root balls, unmated queens (surrogates of fertile queens) were exposed to soil samples from various positions on treated root balls. None of the of the unmated queens exposed to bifenthrin survived. With lambda-cyhalothrin and chlorpyrifos, 10 and 11% of the soil samples had at least one live unmated queen, respectively. The complete colony disinfestation of root balls and death of all unmated queens indicated that the drench plus injection of bifenthrin could be effective in providing quarantine level control of fire ants in large, harvested field-grown nursery plants.

Technical Abstract: There is an imported fire ant (IFA) quarantine in the USA to prevent human assisted spread of the invasive, red imported fire ant (Solenopsis invicta Buren), black imported fire ant (Solenopsis richteri Forel), and the S. invicta × S. richteri hybrid. Quarantine regulated articles, must be treated following approved protocols and must not be infested with IFA queens or reproducing colonies. Large, post-harvest field-grown nursery plants are an infestation risk because they are difficult to treat effectively with approved insecticide treatments of 1) immersing in chlorpyrifos or bifenthrin solutions, or 2) thoroughly drenching root balls with chlorpyrifos. To improve quarantine treatments, the efficacies of disinfesting IFA colonies from trees harvested with large (60-cm diam) root balls were determined among the drenching and injecting (D&I) of a) bifenthrin or, b) lambda-cyhalothrin, c) chlorpyrifos drench standard, and d) water drench (control). Bifenthrin and lambda-cyhalothrin D&I treatments eliminated all IFA colonies in 2-wk, while > 70% of the chlorpyrifos drench-only and control root balls were infested. Bioassays of red IFA female alates (surrogates of newly-mated queens that start new colonies) in soil sampled from various root ball positions receiving the above treatments resulted in no survival of alates exposed to bifenthrin after 10-d. With lambda-cyhalothrin and chlorpyrifos, 10 and 11% of the soil samples had = 1 surviving alate, respectively. The complete IFA colony disinfestation of root balls and the death of all alates in soil samples indicated bifenthrin D&I could provide additional and effective quarantine level control of IFA in large, post-harvest field-grown nursery plants.