204
Gene R. DeFoliart
8.5.1. Salt Marsh Mosquitoes
Ae. sollicitans and Ae. taeniorhynchus are the salt marsh mosquitoes of the
Atlantic and Gulf coasts. Control efforts have traditionally depended on source
reduction-diking, ditching, dredging, and filling of marshlands-supplemented
by the use of adulticides. There is increasing opposition to most types of salt
marsh minipulation, however, despite excellent and painstaking studies showing
that source reduction can be practiced on salt marshes without damage to the
delicate ecology of tidelands and estuaries.
Salt marsh Aedes inhabit the high marsh, while the biota to be protected
utilize the low marsh and the estuaries. Larvicides cannot be applied to the high
marsh because they may be washed into the estuaries by tides and rain. Provost
(1977) advocates that the open-marsh management system developed in New
Jersey (Ferrigno, 1970; Ferrigno and Jobbins, 1968; Ferrigno et ai., 1969) is
applicable with slight modification to salt marshes everywhere. Ditches are dug
only to connect mosquito-breeding depressions to tidewater or to ponds. This
insures that temporary water does not stand long enough for mosquitoes to
develop and permits access of minnows to all parts of the marsh. Permanent
ponds and pools that serve as shrimp nurseries are not connected to the ditching
system. If done properly, ditching increases marsh and estuarine productivity
by expediting the flushing of detritus into the lower marsh and estuary (Provost,
1974).
Impoundments can also be ecologically safe if they are constructed to permit
exchange of impoundment and estuarine waters, permitting movement of aquatic
life, preservation of the natural vegetation, and release of nutrients to the estuary.
The Gumbo Island (Florida) impoundment described by Provost (1974) has
proven completely effective in preventing mosquito development, while not
damaging the normal functioning of the marsh (Provost, 1977).
8.5.2. Aedes vexans
Ae. vexans, the major pest species in the north-central U. S., breeds in
temporarily flooded woods, fields, and river floodplains, from whence it invades
populated areas. Since much of the breeding is on wildlands, source reduction
opportunities are limited. However, the work of Dixon and Brust (1972) is a
good example of how careful surveillance can constitute "source reduction" as
far as reducing the need for insecticides is concerned. They conducted intensive
larval surveys in a perimeter around Winnipeg, Manitoba, and found that only
20-25% of the pools sampled produced mosquitoes. The mosquito-producing
pools totaled only 5 acres out of 5120 acres surveyed, and the area requiring
larval-control measures was only 3% of the uncultivated land area. If treated
Gene R. DeFoliart
8.5.1. Salt Marsh Mosquitoes
Ae. sollicitans and Ae. taeniorhynchus are the salt marsh mosquitoes of the
Atlantic and Gulf coasts. Control efforts have traditionally depended on source
reduction-diking, ditching, dredging, and filling of marshlands-supplemented
by the use of adulticides. There is increasing opposition to most types of salt
marsh minipulation, however, despite excellent and painstaking studies showing
that source reduction can be practiced on salt marshes without damage to the
delicate ecology of tidelands and estuaries.
Salt marsh Aedes inhabit the high marsh, while the biota to be protected
utilize the low marsh and the estuaries. Larvicides cannot be applied to the high
marsh because they may be washed into the estuaries by tides and rain. Provost
(1977) advocates that the open-marsh management system developed in New
Jersey (Ferrigno, 1970; Ferrigno and Jobbins, 1968; Ferrigno et ai., 1969) is
applicable with slight modification to salt marshes everywhere. Ditches are dug
only to connect mosquito-breeding depressions to tidewater or to ponds. This
insures that temporary water does not stand long enough for mosquitoes to
develop and permits access of minnows to all parts of the marsh. Permanent
ponds and pools that serve as shrimp nurseries are not connected to the ditching
system. If done properly, ditching increases marsh and estuarine productivity
by expediting the flushing of detritus into the lower marsh and estuary (Provost,
1974).
Impoundments can also be ecologically safe if they are constructed to permit
exchange of impoundment and estuarine waters, permitting movement of aquatic
life, preservation of the natural vegetation, and release of nutrients to the estuary.
The Gumbo Island (Florida) impoundment described by Provost (1974) has
proven completely effective in preventing mosquito development, while not
damaging the normal functioning of the marsh (Provost, 1977).
8.5.2. Aedes vexans
Ae. vexans, the major pest species in the north-central U. S., breeds in
temporarily flooded woods, fields, and river floodplains, from whence it invades
populated areas. Since much of the breeding is on wildlands, source reduction
opportunities are limited. However, the work of Dixon and Brust (1972) is a
good example of how careful surveillance can constitute "source reduction" as
far as reducing the need for insecticides is concerned. They conducted intensive
larval surveys in a perimeter around Winnipeg, Manitoba, and found that only
20-25% of the pools sampled produced mosquitoes. The mosquito-producing
pools totaled only 5 acres out of 5120 acres surveyed, and the area requiring
larval-control measures was only 3% of the uncultivated land area. If treated