Effects of Impounding and Filling on the Production of Sand Flies (Culicoides) in Florida Salt Marshes.1

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Abstract
As source-reduction methods for mosquito control, filling by dredge and impounding are rapidly replacing ditching in many counties on the Florida East Coast. Studies during 1958 to 60 showed that both filling and impounding also control sand flies (Culicoides spp.) that breed in these marshes. Ditching is not effective against sand flies. An average of only 0.1 larvae/sample was found in soil samples from two fills having an average elevation of only 3.46 feet above mean sea level; an average of 37.4 larvae/sample was found in samples from comparable areas of two nearby untreated marshes. The filled portion of the two marshes studied comprised 93.8% of the total sand fly larval habitat; significant breeding was restricted to the tidal shoreline by the treatment. An average of only 0.1 larvae/sample was found in soil samples from two permanently flooded plots as compared with 6.9 from an adjacent plot that was intermittently flooded and 2.6 from a nearby ditched plot. In the permanently flooded plots, sand fly breeding was controlled in 94% of the total larval habitat. Sand fly larvae at water-edge sites having a steep slope, such as dike banks, were largely confined to a narrow zone at the water's edge; at sites where the slope was less acute, larvae were more widely dispersed, with the largest number occurring 1 to 2 feet above the edge of the water. No free-swimming larvae were found in samples of water dipped from the permanently flooded plots. Culicoides furens (Poey) was the principal species reared from random soil samples.

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