221 - Exploring a cost-effective SIT approach for control of Aedes aegypti in Lake Elsinore, CA  

Abstract: The Sterile Insect Technique (SIT) is rapidly becoming an accepted technology for the control of Aedes aegypti (L. ) in the US and around the world. In summer of 2025, Northwest Mosquito and Vector Control District (NWMVCD) developed a cost-effective SIT pilot program targeting Ae. aegypti in Lake Elsinore, California. Local field-collected Ae. aegypti eggs were provided to Rad Source Technologies, Inc., Buford, GA (Rad Source©), developers of x-ray radiation technologies and mass-rearing of mosquitoes, to create a California Ae. aegypti (Cali strain) colony. NWMVCD purchased adult male Cali strain mosquitoes from Rad Source©, which performed all rearing and x-ray sterilization steps. Prior to field release, the Cali strain mosquitoes were evaluated in-house to assess their longevity and fecundity. Preliminary findings pointed to the operational feasibility of using outsourced sterile males as a cost-effective alternative to in-house rearing and irradiation. The field site consisted of a 20-acre area (three 5-acre treatment plots and one 5-acre control plot) in the geographically isolated McVicker Canyon neighborhood of Lake Elsinore with historical Ae. aegypti abundance data. Routine vector control operations, including pesticide applications when warranted, were performed as usual in all four zones. Eight weekly releases of approximately 24,000 sterile males (equivalent to an application rate of 1600 mosquitoes/acre) were made from July to September. Surveillance trapping using BG Sentinels (n=13) was conducted weekly for 18 weeks to cover time periods both before and after the sterile male releases. Due to low natural abundance of female Ae. aegypti (averaging < 4 per trap night) and highly variable surveillance data, it is difficult to say definitively that sterile males reduced the wild Ae. aegypti population. Nevertheless, NWMVCD demonstrated that SIT can be functionally accessible for most vector control agencies without their own sterile male production facility.