Pesticide‐mediated trophic cascade and an ecological trap for mosquitoes
Claire Duchet,
Gail M. Moraru,
Matthew Spencer,
Kumar Saurav,
Celine Bertrand,
Stephanie Fayolle,
Anna Gershberg Hayoon,
Ronen Shapir,
Laura Steindler,
Leon Blaustein
Affiliations
Claire Duchet
Community Ecology Laboratory Institute of Evolution and Department of Evolutionary & Environmental Biology Faculty of Natural Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Gail M. Moraru
Community Ecology Laboratory Institute of Evolution and Department of Evolutionary & Environmental Biology Faculty of Natural Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Matthew Spencer
School of Environmental Sciences University of Liverpool Liverpool L69 3GP UK
Kumar Saurav
Department of Marine Biology Leon H. Charney School of Marine Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Celine Bertrand
Aix Marseille Univ, Univ Avignon CNRS, IRD, IMBE (Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale), FSE Jérôme Case 431 F‐13397 Marseille Cedex 20 France
Stephanie Fayolle
Aix Marseille Univ, Univ Avignon CNRS, IRD, IMBE (Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale), FSE Jérôme Case 431 F‐13397 Marseille Cedex 20 France
Anna Gershberg Hayoon
Community Ecology Laboratory Institute of Evolution and Department of Evolutionary & Environmental Biology Faculty of Natural Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Ronen Shapir
Community Ecology Laboratory Institute of Evolution and Department of Evolutionary & Environmental Biology Faculty of Natural Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Laura Steindler
Department of Marine Biology Leon H. Charney School of Marine Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Leon Blaustein
Community Ecology Laboratory Institute of Evolution and Department of Evolutionary & Environmental Biology Faculty of Natural Sciences University of Haifa Mt. Carmel Haifa 3498838 Israel
Abstract Broad‐spectrum pesticides can have immediate toxic effects both on target pest species and on non‐target species. They may also have positive residual effects on mosquitoes after pesticide degradation, by altering the community structure, that is, by reducing abundances of mosquito competitors and predators, and via a trophic cascade, which may increase food resources for mosquito larvae. Alternatively, if a pesticide‐mediated trophic cascade results in toxic or inedible algae, the pesticide can act as an ecological trap for some taxa by attracting oviposition in sites where algae are abundant but unsuitable. The present study assessed mosquito oviposition habitat selection, mosquito larval performance, and community structure alterations after applications of various pesticides. The experiment was conducted in outdoor mesocosms assigned to one of four treatments: (1) control, no pesticides; (2) Bacillus thuringiensis var. israelensis (Bti), a narrow‐spectrum bacterium well known for its larvicidal activity on mosquitoes and other dipterans; (3) temephos, an organophosphate mosquito larvicide with community‐wide spectrum effects; and (4) pyriproxyfen, a pyridine‐based insect growth regulator (IGR) class with wide‐spectrum effects. Soon after pesticide application, Culex pipiens oviposition was highest in the control pools. Invertebrate species richness and abundance were strongly reduced in the broad‐spectrum pesticide treatments (temephos and pyriproxyfen) when compared to control. One month after pesticide application, Cx. pipiens oviposition was highest in the pyriproxyfen‐treated pools, although larval survival remained lowest in the pyriproxyfen‐treated pools. Our results suggest that pyriproxyfen causes a chemically mediated trophic cascade and provides an ecological trap, that is, attracting mosquito oviposition due to an altered community structure, but causing high mosquito larval mortality.
