Overview of Pesticide Residues in Stored Pollen and Their Potential
Effect on Bee Colony (Apis mellifera) Losses in Spain

J. BERNAL,1,2 E. GARRIDO-BAILO´ N,3 M. J. DEL NOZAL,1 A. V. GONZA´ LEZ-PORTO,3
R. MARTI´N-HERNA´ NDEZ,3 J. C. DIEGO,1 J. J. JIME´ NEZ,1 J. L. BERNAL,1 AND M. HIGES3

J. Econ. Entomol. 103(6): 1964Ð1971 (2010); DOI: 10.1603/EC10235

ABSTRACT In the last decade, an increase in honey bee (Apis mellifera L.) colony losses has been
reported in several countries. The causes of this decline are still not clear. This study was set out to
evaluate the pesticide residues in stored pollen from honey bee colonies and their possible impact on
honey bee losses in Spain. In total, 1,021 professional apiaries were randomly selected. All pollen
samples were subjected to multiresidue analysis by gas chromatography-mass spectrometry (MS) and
liquid chromatography-MS; moreover, speciÞc methods were applied for neonicotinoids and Þpronil.
A palynological analysis also was carried out to conÞrm the type of foraging crop. Pesticide residues
were detected in 42% of samples collected in spring, and only in 31% of samples collected in autumn.
Fluvalinate and chlorfenvinphos were the most frequently detected pesticides in the analyzed
samples. Fipronil was detected in 3.7% of all the spring samples but never in autumn samples, and
neonicotinoid residues were not detected. More than 47.8% of stored pollen samples belonged to wild
vegetation, and sunßower (Heliantus spp.) pollen was only detected in 10.4% of the samples. A direct
relation between pesticide residues found in stored pollen samples and colony losses was not evident
accordingly to the obtained results. Further studies are necessary to determine the possible role of
the most frequent and abundant pesticides (such as acaricides) and the synergism among them and
with other pathogens more prevalent in Spain.

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