The runnelling method of habitat modification: an environment-focused tool for salt marsh mosquito management

Traditional methods of managing salt marsh mosquitoes focus primarily on maximizing the reduction of mosquito populations, with minimizing environmental impact as a secondary consideration. An environment-oriented approach to salt marsh management for mosquito control, runnelling, is described and compared with other forms of habitat modification such as ditching and Open Marsh Water Management (OMWM). Runnelling alters the salt marsh as little as possible while causing significant reductions in mosquito numbers. The effect of runnelling on the environment was monitored via the following variables: water table level, substrate characteristics (moisture, salinity and pH), vegetation (height and density of each Sporobolus virginicus) and the numbers of mosquito larvae. Runnelling had a statistically significant effect on only two of the seven variables. These were the height of Sporobolus, which increased near runnels, and the number of mosquito larvae, which decreased. The main difference between ditching, OMWM and runnelling lies in the magnitude of the habitat modification. Ditching involves the greatest alteration to the marsh, and runnelling the least. Consequently, runnelling has a smaller effect on the estuarine environment as a whole than does either ditching or OMWM.