Impact of low aerial application rates of Dibrom 14 on potential vectors

Aerial applications designed to assess the impact of low application rates of naled (Dibrom 14) on potential vector species were conducted in 2003 with caged adult Anopheles quadrimaculatus in open grassland at Cecil Airfield in Jacksonville, FL. Offset flight paths of 2,000-6,000 (calculated by the AgDisp aerial application model) and 1,000-ft swath widths were conducted with a Micronair AU4000 rotary atomizer, which provides a several-fold increase in droplets between 7 and 22 microm. Mean volume median diameters of 8.0, 7.8, and 9.4 microm and 290, 506, and 192 droplets per sq cm were observed in the target area with application rates of 0.125, 0.25, and 0.5 fl oz per acre, respectively. The observed mean mortality of caged mosquitoes 12 h posttreatment, corrected for mortality in untreated controls, was 14%, 80%, and 99% at 0.125, 0.25, and 0.5 fl oz per acre, respectively. These results indicate that applications at 0.25 fl oz per acre or less should be avoided and rates greater than 0.5 fl oz may be required for adequate control in canopied habitats and less-than-optimum terrains.