Effects of Bacillus thuringiensis israelensis and spinosad on adult emergence of the non-biting midges Polypedilum nubifer (Skuse) and Tanytarsus curticornis Kieffer (Diptera: Chironomidae) in coastal wetlands.
To optimize their efficacy, some insecticides used for mosquito control are introduced into aquatic ecosystems where mosquito larvae develop (marshes, ponds, sanitation devices) and cannot escape from the treated water. However, this raises the question of possible effects of mosquito larvicides on non-target aquatic species. Bacillus thuringiensis var. israelensis (Bti), which is well-known for its selectivity for Nematocera dipterans, is widely used for mosquito control all over the world. Spinosad, a mixture of spinosyns A and D known as fermentation products of a soil actinomycete (Saccharopolyspora spinosa), is a biological neurotoxic insecticide with a broader action spectrum. It is a candidate larvicide for mosquito control, but some studies showed that it may be toxic to beneficial or non-target species, including non-biting midges. The present study was therefore undertaken to assess the impact of Bti and spinosad on natural populations of Polypedilum nubifer (Skuse) and Tanytarsus curticornis Kieffer (Diptera: Chironomidae) in field enclosures implemented in Mediterranean coastal wetlands. Unlike Bti, spinosad had a strong lethal effect on P. nubifer and seems to affect T. curticornis at presumed recommended rates for field application. Differences in the sensitivity of these two species to spinosad confirm that population dynamics need to be known for a proper assessment of the risk encountered by chironomids in wetlands where larvicide-based mosquito control occurs.
Entente Interdépartementale de Démoustication du Littoral Méditerranéen, 165 avenue Paul-Rimbaud, F-34184 Montpellier, France. Electronic address: cduchet@eid-med.org.
Claire
C
Duchet
Aix Marseille Université, Institut Méditerranéen de Biodiversité et Ecologie Marine et Continentale, UMR CNRS 7263/ IRD-Service 431, Pôle de l'Etoile, 13397 Marseille cedex 20, France.
Evelyne
E
Franquet
INRA, UMR985 Écologie et Santé des Écosystèmes, Équipe Écotoxicologie et Qualité des Milieux Aquatiques, Agrocampus Ouest, 65 rue de Saint Brieuc, F-35042 Rennes, France.
Laurent
L
Lagadic
Entente Interdépartementale de Démoustication du Littoral Méditerranéen, 165 avenue Paul-Rimbaud, F-34184 Montpellier, France.
Christophe
C
Lagneau
D000818:Animals; D001413:Bacillus thuringiensis; D002683:Chironomidae / Q000187:drug effects* / Q000254:growth & development; D004338:Drug Combinations; D007306:Insecticides / Q000633:toxicity*; D018942:Macrolides / Q000633:toxicity*; D009032:Mosquito Control; D011157:Population Dynamics; D053833:Wetlands
D004338:Drug Combinations; D007306:Insecticides; D018942:Macrolides; C415329:spinosad
Biological insecticide; Field enclosure; Mosquito control; Non-biting midge; Non-target invertebrate