Wetland Science

Mosquito control in freshwater wetlands is a difficult and complex issue, but control through a management approach is feasible. Notwithstanding engineering objectives for constructed wetlands, the priority guidelines for mosquito management can be listed as:

1. Wetlands should be deep. The perimeter should be regular, free of vegetation and debris, and steeply sloping.
2. Wetlands that are necessarily shallow should be free of vegetation and edges should be steeply sloping. The interior of the pond should be graded for rapid dewatering.
3. Wetlands that are necessarily shallow and vegetated should have structures to provide for flooding and draining. Pools of deep water should be provided for fish survival.
4. Wetlands that are necessarily shallow and vegetated and cannot be periodically drained, should be maintained with substantial populations of predatory fish.
5. Wetlands which cannot be managed with structural, environmental or biological methods should be treated as required with a recommended control agent.
6. Wetlands and the areas surrounding them, whatever above or other measures are implemented, should be subject to periodic surveillance for mosquito species and abundance using appropriate sampling techniques at an appropriate frequency.

In conclusion, the issue of mosquito production by freshwater wetlands, whether natural or constructed, should be considered on a case by case basis. Expert advice on the potential hazards, nuisance values and health risks, and the options for minimising the mosquito populations, should be sought and carefully considered.

Mosquito control in saline wetlands ( mangroves and saltmarshes) can be complex, and is usually beyond the capacity of an individual. Notwithstanding the difficulties associated with persuading the various levels of government to undertake mosquito management in these sensitive habitats, the general principles for mosquito control in mangrove and saltmarsh areas can be listed as:

1. Tidal flushing within stands of mangroves should be maintained so that stagnant impounded water does not provide mosquito habitat.
2. Natural dewatering of the surface of the saltmarsh should be maintained so that water does not persist in depressions filled by the highest monthly tides.
3. Structural management (channelling/runnelling) of water flow through the mangroves and onto and off the marsh, providing for natural flushing and dewatering, and access for predators, can be effective in reducing mosquito populations and can be environmentally acceptable.
4. Use of biorational control agents, such as bacterial products and growth regulators, to reduce mosquito populations can be effective and environmentally acceptable.

However, and in conclusion, the issue of mosquito production from saline wetlands must be considered on a case by case basis. Expert advice on the relative nuisance values and health risks, and the acceptable and effective options appropriate for particular sites should be sought from relevant experts and carefully considered.