A few years ago a study done in Belgium stated:

In conclusion, our study does not support the involvement
of maize treated with imidacloprid in the
observed mortality-related problems that affect honey
bees in Belgium. However, nutritive scarcity in the
environment must be further studied. The very
large number of samples containing acaricides, especially
ineffective (tau-ßuvalinate) or prohibited
(rotenone, bromopropylate) materials, to control V.
destructor along with apicultural practices highlighted
during beekeeper interviews suggest the inadequacy
of the methods used for mite control.

The authors were

B. K. Nguyen, C. Saegerman, C. Pirard, J. Mignon, J. Widart, B.
Thirionet, F. J. Verheggen, D. Berkvens, E. De Pauw, and E. Haubruge

Their affiliations were

Department of Functional and Evolutionary Entomology,
FUSAGx, 5030 Gembloux, Belgium.

Department of Infectious and Parasitic Diseases, Epidemiology
and Risk analysis applied to the Veterinary Sciences, University of
Liege, 4000 Liege, Belgium.

Laboratory of Mass Spectrometry (CART), University of Liege,
4000 Liege, Belgium.

Department of Animal Health, Institute of Tropical Medicine,
2000 Antwerp, Belgium.

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