Synergistic mortality between a neonicotinoid insecticide and an ergosterol-biosynthesis-inhibiting fungicide in three bee species.
BACKGROUND
Neonicotinoid insecticides have been identified as an important factor contributing to bee diversity declines. Nonetheless, uncertainties remain about their impact under field conditions. Most studies have been conducted on Apis mellifera and tested single compounds. However, in agricultural environments, bees are often exposed to multiple pesticides. We explore the synergistic mortality between a neonicotinoid (clothianidin) and an ergosterol-biosynthesis-inhibiting fungicide (propiconazole) in three bee species (A. mellifera, Bombus terrestris, Osmia bicornis) following oral exposure in the laboratory.


RESULTS
We developed a new approach based on the binomial proportion test to analyse synergistic interactions. We estimated uptake of clothianidin per foraging bout in honey bees foraging on seed-coated rapeseed fields. We found significant synergistic mortality in all three bee species exposed to non-lethal doses of propiconazole and their respective LD10of clothianidin. Significant synergism was only found at the first assessment times in A. mellifera (4 and 24 h) and B. terrestris (4 h), but persisted throughout the experiment (96 h) in O. bicornis. O. bicornis was also the most sensitive species to clothianidin.


CONCLUSIONS
Our results underscore the importance to test pesticide combinations likely to occur in agricultural environments, and to include several bee species in environmental risk assessment schemes. © 2016 Society of Chemical Industry.
Dipartimento di Scienze Agrarie, Università di Bologna, Bologna, Italy.
Fabio
http://orcid.org/0000-0002-2845-8297
F
Sgolastra
CREA-API, Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria, Unità di Ricerca in Apicoltura e Bachicoltura, Bologna, Italy.
Piotr
P
Medrzycki
CREA-API, Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria, Unità di Ricerca in Apicoltura e Bachicoltura, Bologna, Italy.
Laura
L
Bortolotti
Dipartimento di Scienze Agrarie, Università di Bologna, Bologna, Italy.
Maria Teresa
MT
Renzi
Dipartimento di Scienze Agrarie, Università di Bologna, Bologna, Italy.
Simone
S
Tosi
CREA-API, Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria, Unità di Ricerca in Apicoltura e Bachicoltura, Bologna, Italy.|Dipartimento di Scienze Biologiche, Geologiche ed Ambientali, Università di Bologna, Bologna, Italy.
Gherardo
G
Bogo
Research Institute of Horticulture, Apiculture Division, Puławy, Poland.
Dariusz
D
Teper
Dipartimento di Scienze Agrarie, Università di Bologna, Bologna, Italy.
Claudio
C
Porrini
CREAF, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Roberto
R
Molowny-Horas
CREAF, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Jordi
J
Bosch
D000818:Animals; D001516:Bees / Q000187:drug effects*; D029741:Brassica rapa; D005659:Fungicides, Industrial; D006146:Guanidines; D007306:Insecticides; D000073943:Neonicotinoids; D013844:Thiazoles; D014230:Triazoles
D005659:Fungicides, Industrial; D006146:Guanidines; D007306:Insecticides; D000073943:Neonicotinoids; D013844:Thiazoles; D014230:Triazoles; C045950:propiconazole; C480342:clothianidin
Apis mellifera; Bombus terrestris; Osmia bicornis; binomial proportion test; clothianidin; field-realistic dose; propiconazole; synergism