more people within range of mosquitoes and increase the pressure on 

 local government to institute controls. 



Saltmarsh mosquitoes are controlled by making saltmarsh habitat 

 unsuitable for breeding or by killing insects directly. In the first 

 method, periodic fluctuations in water levels that enable mosquitoes 

 to breed are eliminated. This is accomplished by filling, so that 

 water never stands on the marsh, by ditching, so that water drains 

 from the surface within 2-3 days, or by flooding, so that water com- 

 pletely covers the marsh during the breeding season [139]. In the 

 second method, larvacides or adulticides are sprayed over the 

 marsh. 



Different control techniques cause different types of ecological 

 disturbance. The habitat alteration method may severely impair the 

 productivity and habitat qualities of the marsh if not done properly. 

 The use of pesticides, on the other hand, endangers fish and wildlife 

 directly. 



Past practices such as marsh filling or extensive drainage ditching 

 in a grid pattern, both of which have long-term adverse impacts, are no 

 longer considered acceptable methods of pest control. Massive pesticide 

 application on a routine basis is also discouraged. Planned water manage- 

 ment programs have begun to be recognized as appropriate control 

 alternatives that provide environmental benefits (Figure 45). 



Water level management provides the most effective control 

 of salt-marsh mosquitoes with the least ecological disruption. Water 

 level management may cost more initially than direct control by pesticides, 

 but provides long-term solutions that are not only much better ecologically, 

 but often cheaper over a number of years. In addition to providing 

 effective mosquito control, water management can enhance the flow of 

 water through the marsh, increase marsh productivity, and provide water- 

 fowl habitat. 



Coastal wetlands in their natural state are recognized as having 

 high value. The high productivity levels that existed previous to 

 impoundment are difficult to maintain without the normal water level 

 fluctuations and the resultant water circulation and exchange [80]. 



Diked impoundments cause the same potential disturbances of water 

 flow patterns as flood control dikes and levees. Lower marsh zones and 

 coastal water systems downstream from the impoundment are deprived of 

 freshwater inflow, resulting in changes in salinity, nutrient and sedi- 

 ment balances. 



The adverse impacts are likely to be highest when areas are impound- 

 ed for purposes other than wildlife management. Wildlife impoundments 

 are usually planned and designed to minimize adverse effects. If the 



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