Potential of Outdoor Ultra-Low–Volume Aerosol and Thermal Fog to Suppress the Dengue Vector,Aedes aegypti, Inside Dwellings

Abstract

A field study investigated penetration of outdoor ground ultra-low–volume (ULV) aerosol and thermal fog adulticide applications into a dwelling to control the dengue vector Aedes aegypti (L). Four applications of Kontrol 4-4 (4.6% permethrin active ingredient [AI], 4.6% piperonyl butoxide) at the maximum label rate were made at 25–30 m in front of a house at Camp Blanding Joint Training Center, Starke, FL, during summer 2016. The ULV sprayer and thermal fogger nozzles were oriented horizontally, and vehicle travel speeds were 16 and 24 km/h, respectively. All doors and windows of the house were left open. Spray efficacy was assessed using caged female mosquitoes positioned 30 cm above ground, outside and inside of the house. Interior cages were placed in open areas and cryptic sites (i.e., in a closet or cardboard box). A spinner holding 2 rods sized 3 mm × 75 mm was deployed next to each cage (except cryptic sites) to sample droplets and to quantify AI deposition. Thirty minutes after application, cages were removed, slides collected, and mosquitoes transferred to clean cages in the laboratory where mortality was assessed at 24 h posttreatment. The ULV application to the south side of the house produced 100% mortality in outdoor and indoor cages and 24% mortality at cryptic sites. Similarly applied thermal fog resulted in 85% mortality outdoors, 34% indoors, and only 4% in cages at cryptic sites. Application of either method from the west resulted in 19–61% mortality outdoors and 0.5–6.5% indoors. Droplet volume median diameter (Dv0.5) on rods from the ULV application was significantly larger compared with the thermal fogger outdoors, but similar indoors. Outdoors and indoors, the AI deposition from ULV was significantly higher than from thermal fog. Our results show the potential for controlling dengue vectors inside houses with outdoor ground ULV applications in areas where doors and windows are left open for ventilation.

Semi-field evaluation of the space spray efficacy of Fludora Co-Max EW against wild insecticide-resistant Aedes aegypti and Culex quinquefasciatus mosquito populations from Abidjan, Côte d’Ivoire

“…aegypti mortality rates maximal (100%) at up to 25 m, decreasing, while remaining above 90% up to 50 m, and 80% up to 100 m. In contrast, the mortality rates of K-Othrine EC rapidly dropped down below 80% from 25 m and continued to decrease at up to 100 m. In Cx. quinquefasciatus, Fludora Co-Max EW mortality rates varied between 100% at 10 m and 98% at 100 m, while K-Othrine EC induced mortality rates were 100% at 10 m and decreased to 87% at 100 m. The capacity of Fludora Co-Max EW to kill mosquitoes over long distance is consistent with the results reported by Farooq et al [10] where ULV application of Kontrol (permethrin and piperonyl butoxide) produced 100% mortality in Ae. aegypti outdoors in Starke, Florida, USA.…”

“…quinquefasciatus . Such lower mortality with outdoor TF (85%) compared to outdoor ULV (100%) was observed with Kontrol in Stake, USA [10]. The reduction in Fludora Co-Max EW mortality with TF outdoors might be attributed to thermal effect (i.e.…”

“…aegypti outdoors in Starke, Florida, USA. However, Kontrol contains a synergist and the distance checkpoints were shorter (25-30 m) [10] compared with the Fludora Co-Max EW effect distance checkpoints (10-100 m). Moreover, Fludora Co-Max EW kill mosquitoes up to significantly longer distance compared to K-Othrine EC.…”

Emerging mosquito resistance to piperonyl butoxide-synergized pyrethroid insecticide and its mechanism

“…However, results are comparable under the same experimental conditions. Field applications of ULV spraying show large variations in reductions in mosquito densities [56]; it is unknown whether the low effectiveness is due to mosquitoes’ tolerance to insecticides, spraying methods, or the coverage of spraying, as it is infeasible for aerial/ground sprayings to cover every mosquito [56,60]. Furthermore, field environmental conditions also affect spraying efficacy [56].…”

“…ULV spraying of PBO-synergized pyrethroids such as Aqualuer® 20-20 has been extensively evaluated [56,57]. Although semi-field (caged) experiments using direct spraying can be adapted to evaluate the efficacy of PBO-synergized pyrethroids [57,58], the outcomes are affected by many factors including the specifications of sprayers, travel distance of droplets, and environmental conditions (e.g., wind speed and direction) [56][57][58][59][60], which likely contributed to inter-experimental variations in mosquito mortality [56]. Therefore, we did not conduct direct spraying experiments.…”