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A six-year study of insect emergence from temporary flooded wetlands in central Sweden, with and without Bti-based mosquito control
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
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2010 (English)In: Bulletin of entomological research, ISSN 0007-4853, E-ISSN 1475-2670, Vol. 100, no 6, 715-725 p.Article in journal (Refereed) Published
Abstract [en]

In temporary wetlands in the River Dalalven floodplains, recurrent but irregular floods induce massive hatching of the flood-water mosquito Aedes sticticus, which causes enormous nuisance. Flood-water mosquito control using the biological larvicide Bacillus thuringiensis var. israelensis (Bti) was commenced in parts of the floodplains during 2002, and here we report the first six years of full-season monitoring of general insect emergence from temporary wetlands with and without treatment. Emergence traps, which were emptied weekly, were used from May to September each year. A total of 137,153 insects of 13 taxonomic orders were collected. Diptera was highly dominating and especially the sub-order Nematocera with 18 families was a very prominent taxon. Bti-treatment effects were analysed by taxonomic order, by sub-order in Diptera and Hemiptera, and by family for Nematocera and Coleoptera for the whole study period. We found no significant negative effects of Bti treatments on the production of insects by taxonomic order, with the exception of Coleoptera in the long term. However, no significant negative effects were found for the Coleoptera families, neither in the short term nor in the long term. There was no significant negative treatment effect on Nematocera production, neither when analyzed for the whole sub-order nor when analyzed by family. However, abundance of Ceratopogonidae was significantly higher in experimental than in reference wetlands. We conclude that Bti-treatment effects on insect production may be minute in comparison to other environmental factors structuring the insect fauna of the temporary wetlands studied.

Place, publisher, year, edition, pages
2010. Vol. 100, no 6, 715-725 p.
Keyword [en]
wetland insects, insect production, Bti, temporary wetlands
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-135365DOI: 10.1017/S0007485310000076ISI: 000284012200010OAI: oai:DiVA.org:uu-135365DiVA: diva2:375219
Available from: 2010-12-07 Created: 2010-12-06 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Long Term Studies of Insect Abundances in Temporary Wetlands in Relation to Hydrology, Predation and Bti
Open this publication in new window or tab >>Long Term Studies of Insect Abundances in Temporary Wetlands in Relation to Hydrology, Predation and Bti
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Long-term insect abundances have been studied to investigate factors structuring the insect communities of the temporary wetlands around the River Dalälven floodplain. In the wet meadows and swamps in the River Dalälven floodplains recurrent floods are the ultimate prerequisite for high production of floodwater mosquitoes. In the larval stages these make up a superabundant potential prey for aquatic predatory insects while as adults they become nuisance for people and animals. Mosquito control with Bacillus thuringiensis israelensis (Bti) has been carried out in parts of the floodplain wetlands since 2002. This study investigate potential long-term effects of Bti on non-target insects in general, and non-biting midges (Diptera: Chironomidae) and aquatic predator insects in special in 10 temporary wetlands. Diving-beetles (Coleoptera: Dytiscidae) were the most common aquatic predatory insects in temporary flooded wetlands, and we found no indications that diving-beetles were negatively affected by mosquito larvae reduction with Bti-treatments. Non-target Bti-effects on the insect community in general, measured as increase or decrease of insect abundances, in general showed no effects of Bti except for Coleoptera. The non-biting midges were studied on species level, since this taxon previously has been associated with negative Bti non-target effects in the short-term. We found no reduced production of chironomids at neither family, nor subfamily level in Bti-treated as compared to untreated wetlands. We conclude that other factors than the occasional Bti-treatments dominate in structuring the chironomids fauna. For example, hydrology measured as floods and hydroperiod had substantial impact on insect emergence Increased hydroperiod was associated with lower insect emergence for the majority of the studied taxa, indicating an insect fauna adapted more to terrestrial conditions. In the final study, we developed and applied a molecular method to study interspecific predator – prey relationships between medium-sized diving beetles and floodwater mosquito larvae. Gut content analyses showed that floodwater mosquito larvae are a regular, but limited, part of the diet of medium-sized diving beetles. This thesis is one of the first long-term studies of insects of temporary wetlands in relation to mosquito control actions. The results indicate that hydrology is one of the major factors influencing and structuring the insect communities of the temporary flooded wetlands in the River Dalälven floodplains, and that mosquito control actions with Bti only have marginal effect on insect abundances.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 48 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1080
Keyword
floodwater mosquitoes, mosquito control, predation, aquatic insects
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-207841 (URN)978-91-554-8762-1 (ISBN)
Public defence
2013-11-08, Lindahlsalen, Evolutionsbiologiskt Centrum, Norbyvägen 18 B, Uppsala, 10:00 (English)
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Supervisors
Available from: 2013-10-18 Created: 2013-09-19 Last updated: 2014-01-23

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