DUET™ was evaluated against field-collected mosquito populations in St. John's County, FL, under laboratory and field conditions. Ten serial dilutions ranging from 22 to 2.2E^-08 µg/ml of the product were tested against Aedes albopictus, Ae. taeniorhynchus, Culex quinquefasciatus, and Psorophora columbiae. At 0.0022 µg/ml, 100% mortality was recorded for all species except for Cx. quinquefasciatus. The 50% lethal concentration value for Cx. quinquefasciatus was 0.0029 µg/ml (CI  =  0.00069 to 0.013). At the lowest dilution (2.2E-08 µg/ml) evaluated, Ae. albopictus, Ae. taeniorhynchus, and Ps. columbiae showed >50% mortality. Ground ultralow-volume application of DUET resulted in overall average mortality of 87% of field-collected Cx. quinquefasciatus mosquitoes. There was a significant difference in mortality based on the distance of the caged mosquitoes (P < 0.05). However, mortality was >70% at the farthest distance from the application (106 m).