Investigations of Methodologies for Management of Mosquito Populations in Phosphate Mining Areas
Mosquitoes capable of transmitting St. Louis and eastern equine encephalitis viruses and of producing pestiferous infestations are found in excessive numbers throughout active and inactive phosphate mining areas of Polk County. It is estimated that approximately 100 square miles of old and new mining operations in the county are capable of supporting mosquitoes. It is also estimated that, depending on weather conditions, 50-75 percent of the mosquitoes present in Polk County in a given period are produced in aquatic habitats associated with active or inactive phosphate mining operations.
The purpose of this project was to make a comprehensive study and comparison of the biological parameters of potential disease bearing and pest mosquitoes associated with active, inactive and reclaimed phosphate mining areas with those in natural wetlands. Subsequently, it was hoped to relate the biological findings to control methodology so that they could become integrated, practically and economically, into an environmentally acceptable mosquito control program with minimal impact on current mining practices or costs.
The research effort was concentrated on the two groups of man-biting mosquitoes that create the majority of the problems associated with phosphate mining. These two groups are the Mansonia group, comprised of three species, Coquillettidia perturbans, Mansonia titillans and Mansonia dyari, and the Culex group, composed of Culex nigripalpus and Culex salinarius. The emphasis of the research was on developing biological control mechanisms and methods of habitat manipulation rather than chemical control.
The objectives were addressed in two phases, the first of which was a general survey of mosquito populations in the phosphate district. Immature mosquitoes were collected from floating plants 1) by pulling plants and examining the roots and 2) with the area sampler, which was developed during this study. Rooted vegetation was sampled by another method, the suction probe, which was developed specifically for this purpose during this study. Adult production was monitored with emergence traps and biting adults were collected with carbon dioxide-baited CDC miniature light traps.
The second phase of the project was a series of projects each of which addressed a specific characteristic or behavior of the insects and their environment. The studies involved measurements of the parameters that are essential for developing effective mosquito control strategies or which had a potential for yielding a control strategy.