Location: Floral and Nursery Plants Research
Project Number: 8020-21000-086-005-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 22, 2023
End Date: Sep 21, 2028
The objective of this project is to develop improved treatment options for imported fire ant to support new Federal Imported Fire Ant Quarantine regulations.
This new NACA between TSU and the USDA-ARS National Arboretum will support replicated research trials to develop imported fire ant (IFA) treatment options for the safe movement of field-grown nursery plants. To date, research has focused on the development of post-harvest pyrethroid drench and injection combination treatments for balled and burlapped (B&B) field-grown plants or in-field pre-harvest individual tree treatments (PITT). Injection protocols were added to post-harvest treatments because federal and state research indicated drenches alone would not control ‘large’ pre-existing IFA colonies. However, injection treatments add an additional treatment step and cost for producers that complicates plant certification. This project will perform research to evaluate B&B drenches without injection for controlling newly mated queens (NMQ) (simulated by female alates) and small fragmented colonies. Both NMQ and small colonies occur near the surface of field plants but are difficult to impossible for producers to detect. However, NMQ and small colony proximity to the surface increases the likelihood a drench treatment alone will be sufficient for plant certification so that more complicated treatment protocols like injection (or dip immersion) can be reserved for plants with large and obvious colonies in the harvest zone. Thus, research will evaluate toxicity of drench treated root ball soil at different penetration depths for controlling small, fragmented colonies and female alates (NMQ substitutes). For PITT treatments, lambda-cyhalothrin has been evaluated to determine optimal rate and longevity, but additional promising pyrethroids like bifenthrin need to be evaluated by this method. The current lambda-cyhalothrin PITT option will likely require at least 7 days of exposure period to certify plants because live moribund ants can remain for multiple days on the surface following treatment. Additional research is needed to determine if moribund ants can recover from PITT treatments and pose a quarantine risk or if these moribund ants are going to ultimately die from treatments. Likewise, other treatments known to kill fire ants by contact (e.g., nootka oil) need evaluation for quick post-treatment elimination of moribund ants. These research approaches are needed to support approvals of treatments that are under USDA-APHIS consideration as nursery quarantine certification treatments.