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The lake trapping was continued twice monthly from February 1991, two years after the first filling of the stage 2A reservoir, until June 1993. The trapping locality at Toonpan was essentially the same as for the 1984–85 studies except that for Big Bay was moved a few hundred metres up the incline. Because the expansion from stage 1 to 2A involved extensive clearing of marginal scrub, grassland and forest, almost total control of five mosquito species utilizing tree holes and plant axils (Aedes alboscutellaris, Aedes mallochi, Aedes purpureus, Aedes quasirubithorax) or shaded pools (Uranotaenia nivipes) occurred. The transformation of temporary wetland with ti-trees (Melaleuca spp.), lilies (Nymphoides indica, Nymphaea gigantea) and submerged plants into an unvegetated muddy foreshore similarly reduced Mansonia spp. and Coquillettidia crassipes, whose larvae depend on attachment to arenchymatous or lacunate macrophytes. Larvae of these genera have pointed reinforced tips to their siphons which are used to pierce these plants to breathe. Because of the devastating nature of the inundation and the time required for new breeding habitat to re-establish, mosquito populations increased through to the end of 1993 but the mean abundance of adult Culex annulirostris had not changed significantly from stage 1 levels. The trend for this species and for Anopheles annulipes was upward, and one can only speculate on population levels when the marginal vegetation has fully established. Due to the extensive loss of marginal vegetation and the creation of expanses of shallow muddy pools, especially towards Toonpan, Anopheles amictus and Aedes normanensis populations increased by 36-fold and 282-fold, respectively (Figure 9.2). The ramifications of this are interesting as Aedes normanensis is well recognized as a vector of Ross River virus and Murray Valley encephalitis, especially inland where Anopheles amictus (probably another species complex) has been the source of Ross River, Barmah Forest and Edge Hill viruses. Control of mosquitoes is usually directed at removal of breeding habitat (source reduction) or aimed at larvae which often aggregate in large numbers in discrete sites. Aedes normanensis is ephemeral and its desiccation-resistant eggs characteristically hatch in response to wet season rainfall filling up temporary pools. Plague numbers appear one month and may be gone the next. More accurate definition of these breeding sites, particularly at Toonpan, Antill Creek and Ross River, is required before control options can be considered. As already mentioned, the clearing process created vast expanses of bare muddy pools, particularly at the north-eastern end (e.g. Toonpan). As the lake gradually receded during the dry season, ideal breeding sites were created and populations increased through spring (from September) and also in the late wet season (March to April) when dry sites were refilled by rainfall. Thus, although the land clearing had benefits in eliminating tropical itch mites and some minor mosquito species, it probably paved the way for population growth of Aedes normanensis and Anopheles amictus. This could possibly be considered a dubious swap, although time will tell. Little is known of their biology and their flight range, the latter being of obvious importance to recreational activity at the other end of the lake. Fortunately, however, they are mainly active at night.
DOI link for The lake trapping was continued twice monthly from February 1991, two years after the first filling of the stage 2A reservoir, until June 1993. The trapping locality at Toonpan was essentially the same as for the 1984–85 studies except that for Big Bay was moved a few hundred metres up the incline. Because the expansion from stage 1 to 2A involved extensive clearing of marginal scrub, grassland and forest, almost total control of five mosquito species utilizing tree holes and plant axils (Aedes alboscutellaris, Aedes mallochi, Aedes purpureus, Aedes quasirubithorax) or shaded pools (Uranotaenia nivipes) occurred. The transformation of temporary wetland with ti-trees (Melaleuca spp.), lilies (Nymphoides indica, Nymphaea gigantea) and submerged plants into an unvegetated muddy foreshore similarly reduced Mansonia spp. and Coquillettidia crassipes, whose larvae depend on attachment to arenchymatous or lacunate macrophytes. Larvae of these genera have pointed reinforced tips to their siphons which are used to pierce these plants to breathe. Because of the devastating nature of the inundation and the time required for new breeding habitat to re-establish, mosquito populations increased through to the end of 1993 but the mean abundance of adult Culex annulirostris had not changed significantly from stage 1 levels. The trend for this species and for Anopheles annulipes was upward, and one can only speculate on population levels when the marginal vegetation has fully established. Due to the extensive loss of marginal vegetation and the creation of expanses of shallow muddy pools, especially towards Toonpan, Anopheles amictus and Aedes normanensis populations increased by 36-fold and 282-fold, respectively (Figure 9.2). The ramifications of this are interesting as Aedes normanensis is well recognized as a vector of Ross River virus and Murray Valley encephalitis, especially inland where Anopheles amictus (probably another species complex) has been the source of Ross River, Barmah Forest and Edge Hill viruses. Control of mosquitoes is usually directed at removal of breeding habitat (source reduction) or aimed at larvae which often aggregate in large numbers in discrete sites. Aedes normanensis is ephemeral and its desiccation-resistant eggs characteristically hatch in response to wet season rainfall filling up temporary pools. Plague numbers appear one month and may be gone the next. More accurate definition of these breeding sites, particularly at Toonpan, Antill Creek and Ross River, is required before control options can be considered. As already mentioned, the clearing process created vast expanses of bare muddy pools, particularly at the north-eastern end (e.g. Toonpan). As the lake gradually receded during the dry season, ideal breeding sites were created and populations increased through spring (from September) and also in the late wet season (March to April) when dry sites were refilled by rainfall. Thus, although the land clearing had benefits in eliminating tropical itch mites and some minor mosquito species, it probably paved the way for population growth of Aedes normanensis and Anopheles amictus. This could possibly be considered a dubious swap, although time will tell. Little is known of their biology and their flight range, the latter being of obvious importance to recreational activity at the other end of the lake. Fortunately, however, they are mainly active at night.
The lake trapping was continued twice monthly from February 1991, two years after the first filling of the stage 2A reservoir, until June 1993. The trapping locality at Toonpan was essentially the same as for the 1984–85 studies except that for Big Bay was moved a few hundred metres up the incline. Because the expansion from stage 1 to 2A involved extensive clearing of marginal scrub, grassland and forest, almost total control of five mosquito species utilizing tree holes and plant axils (Aedes alboscutellaris, Aedes mallochi, Aedes purpureus, Aedes quasirubithorax) or shaded pools (Uranotaenia nivipes) occurred. The transformation of temporary wetland with ti-trees (Melaleuca spp.), lilies (Nymphoides indica, Nymphaea gigantea) and submerged plants into an unvegetated muddy foreshore similarly reduced Mansonia spp. and Coquillettidia crassipes, whose larvae depend on attachment to arenchymatous or lacunate macrophytes. Larvae of these genera have pointed reinforced tips to their siphons which are used to pierce these plants to breathe. Because of the devastating nature of the inundation and the time required for new breeding habitat to re-establish, mosquito populations increased through to the end of 1993 but the mean abundance of adult Culex annulirostris had not changed significantly from stage 1 levels. The trend for this species and for Anopheles annulipes was upward, and one can only speculate on population levels when the marginal vegetation has fully established. Due to the extensive loss of marginal vegetation and the creation of expanses of shallow muddy pools, especially towards Toonpan, Anopheles amictus and Aedes normanensis populations increased by 36-fold and 282-fold, respectively (Figure 9.2). The ramifications of this are interesting as Aedes normanensis is well recognized as a vector of Ross River virus and Murray Valley encephalitis, especially inland where Anopheles amictus (probably another species complex) has been the source of Ross River, Barmah Forest and Edge Hill viruses. Control of mosquitoes is usually directed at removal of breeding habitat (source reduction) or aimed at larvae which often aggregate in large numbers in discrete sites. Aedes normanensis is ephemeral and its desiccation-resistant eggs characteristically hatch in response to wet season rainfall filling up temporary pools. Plague numbers appear one month and may be gone the next. More accurate definition of these breeding sites, particularly at Toonpan, Antill Creek and Ross River, is required before control options can be considered. As already mentioned, the clearing process created vast expanses of bare muddy pools, particularly at the north-eastern end (e.g. Toonpan). As the lake gradually receded during the dry season, ideal breeding sites were created and populations increased through spring (from September) and also in the late wet season (March to April) when dry sites were refilled by rainfall. Thus, although the land clearing had benefits in eliminating tropical itch mites and some minor mosquito species, it probably paved the way for population growth of Aedes normanensis and Anopheles amictus. This could possibly be considered a dubious swap, although time will tell. Little is known of their biology and their flight range, the latter being of obvious importance to recreational activity at the other end of the lake. Fortunately, however, they are mainly active at night.
ABSTRACT