The effectiveness of spinosad for larval mosquito control is summarized based on available published literature and some heretofore unpublished studies. Spinosad is highly active against larvae of all mosquito species tested thus far. It is effective at similar dosages for all larval mosquito instars, with peak cumulative mortality occurring at 72 h posttreatment. More studies are needed to fully define spinosad's ovicidal properties and its impact on the pupal stage. High levels of organic matter and full sunlight are both factors that can negatively impact spinosad efficacy and longevity and should be considered when making use rate and retreatment decisions. Studies clearly show that spinosad technical active ingredient and current crop formulations are suboptimal for larval mosquito control and underrepresent spinosad's true activity. A series of spinosad formulations specialized for larval mosquito control will be sold commercially. Prior to its launch and widespread use, there is a need for additional baseline studies to clarify the natural geographic variation in susceptibility of field mosquito populations. Spinosad represents a new and effective natural product for the integrated management of larval mosquitoes. It possesses a unique mode of action not shared by any other insecticide and is shown to be minimally disruptive to most nontarget species tested thus far at its proposed field use rates.

Simulated raindrops, 4 or 5 mm in diameter, fell 13 m onto target water films, with Pseudocercosporella herpotrichoides spores incorporated into either drops or targets. Resulting splash droplets were collected on fixed photographic film and numbers of droplets, spore‐carrying droplets and spores determined. The patterns of dispersal of splash droplets, spore‐carrying droplets and spores with distance and droplet size were similar for 4 mm and 5 mm incident drops with spores incorporated into either targets or drops. Numbers of droplets, spore‐carrying droplets and spores decreased with increasing distance from targets and none were collected at 1 m. However, more spores were dispersed by 5 mm than by 4 mm drops and with spores in targets than with spores in incident drops. Whereas most splash droplets were in the smallest size category (0–100 μm), most spore‐carrying droplets were 200–400 μm and most spores were in droplets with diameter greater than 1000 μm. Regressions of square root (number of spores) on droplet diameter were significant (p < 0.001) in all cases. The slopes of regression lines were greater when spores were in targets than when they were in incident drops. Splash droplets were collected up to a height of 70 cm, with most between 15 and 20 cm. The dye experiment showed that most splash droplets contained liquid from both incident drop and target film.

An improved method for the sampling of splash droplets carrying fungal spores uses fixed photographic film. Droplets left clear, permanent traces within which spores were easily visible. The droplet spread factor was constant because the gelatine layer was uniform. A comparison of estimates of the numbers of splash droplets, spore‐carrying droplets and spores dispersed by a 5 mm drop falling onto a spore suspension (depth 0.5 mm) with those obtained by other workers demonstrated the reliability of this method. The accuracy was improved by semi‐automatic analysis of the spore‐carrying splash droplet traces with an image‐analysing computer.

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