1a. Objectives (from AD-416):
To determine the feasibility of using a bait formulation to deliver double stranded RNA (dsRNA) complimentary to the yolk protein receptor (VgR) specific to fire ant queens to stop egg-laying.
1b. Approach (from AD-416):
1) Design dsRNA to VgR from the fire ant. 2) Synthesize a dsRNA VgR that is stable and transportable across the ant digestive system via aliphatic-PEG polymer technology (NC State University patent pending). 3) Evaluate the activity of injected VgR dsRNA versus aliphatic PEG dsRNA on Vg synthesis and egg laying in fire ant queens. 4) Evaluate effects of VgR dsRNA versus aliphatic PEG dsRNA provided in nectar or other food substances by colony feeding on Vg synthesis and egg laying in fire ant queens.
3. Progress Report:
These results directly support and correspond to inhouse project objective 4: Develop integrated pest management plans that utilize available control methods, perform comprehensive risk assessment, and that can be adapted to specific stakeholder needs, including local eradication. NCSU has extracted mRNA from fire ant queen, designed polymerase chain reaction (PCR) primers for the yolk protein (Vg) receptor (VgR) in fire ants, and has successfully amplified the fire ant VgR message. Sufficient dsRNA has been synthesized for testing the oral effect of this construct for preventing egg production in queens. ARS conducted bioassays utilizing queens from incipient colonies and individual newly-mated queens to assess the effects of dsRNA solutions. Withholding water from queens resulted in the imbibing dsRNA droplets but it was not as consistent as water droplets. With queens that did imbibe, no reductions in egg laying were observed. As expected, consistent delivery of a sufficient quantity of dsRNA to the queens is a hurdle that will require further research. Observed aversion to the dsRNA solution may be attributed to the salts in the buffer solution. Testing of dsRNA constructs formulated in sugar solution are currently being tested.