Volume 25 / January 2016

Pinellas County Single-brood Trials Yield

Asynchronous, single-brood floodwater mosquitoes present a unique set of challenges in Florida’s Pinellas County. Not only do larvae within the Aedes and Culex populations hatch and develop at different times and rates, the variability of flood patterns exacerbates the issue.

In February 2015, Valent BioSciences Corporation introduced VectoPrime® FG as an innovative means to combat these challenges. Given its year-round battle with floodwater species, Pinellas County was a natural location to put the technology to the test under field conditions. VectoPrime is formulated with BioFuse® technology to provide a specific ratio of Bacillus thuringiensis spp. israelensis Strain AM65-52 and (S)-methoprene for operational flexibility with a wider application window.

Investigators conducted two trials: 1) a microcosm trial using buckets; and 2) a field trial conducted in the salt marsh ecosystems in the county.


Tests were conducted in five-gallon buckets each containing 12 inches of water infused with rabbit food. Eight treatments were made: three treated buckets of L1–L2 instars plus a control, and three buckets of L3–L4 instars plus a control. There were three replicates per treatment. Each bucket received approximately 100 field collected larvae and treated buckets received VectoPrime® FG at the rate of 5 lb per acre. For the assessment, 10 dips were taken and the number of live and dead larvae were counted every two hours from 0 until 12 hours, then again at 24 and 48 hours.

Key results: Nearly all of the Aedes larvae (all instars) died in the first eight hours post-application, whereas nearly all of the Culex larvae died in the first 10 hours. There was no significant mortality in the untreated control bucket.


Tests were conducted within a 48.5-acre section of salt marsh ecosystem chosen by the county. A control site, not connected although present within the county, was established away from the treatment area. Four 200-foot sampling transects were situated away from the border of the treated area and perpendicular to expected aircraft flight lines, and marked with flags. VectoPrime FG was applied aerially at 5 lb per acre to the treatment site. Deposit of VectoPrime FG was verified by four receiving buckets placed evenly along each transect. For the assessment, five dips were taken within a 1-meter radius of each bucket to obtain 20 dips per transect. The larvae were collected and counted by instar at 24, 48, and 72 hours.

Key results: Only eight dipping locations contained larvae and hence only these dipping locations were used for efficacy assessment. The buckets placed in the flagged locations verified that VectoPrime reached all eight locations. No living Aedes or Culex larvae were found 24 or 48 hours post-application in any of the eight dipping locations, indicating 100% mortality (see Figure 1). Larvae were collected in only three of the dipping locations 72 hours post-application.